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A phase transformation of a metastable Zr2Ni intermetallic crystalline phase to vitrify was studied with molecular dynamics (MD) simulations based on a plastic crystal model (PCM), which utilizes the orientational disorder of molecules of plastic crystals in a class of soft matter. The simulation results showed that computational operations in MD-PCM for the random rotations of the clusters in the crystalline phase around their center of gravity and subsequent annealing lead to form a dense random packing structure from the metastable Zr2Ni phase. These randomly-rotated clusters provide high degrees of freedom in terms of atomic positions, which results in enhancing the glass-forming ability of the alloy. The critical fraction of the number of rotated clusters for forming the glassy phase (f(c)(R)) is evaluated to be 0.75-0.80. Thus, the critical fraction of the number of un-rotated clusters (f(c)(U)=1-f(c)(R)) is close to the critical concentration of site percolation for metallic materials. The mechanism of the metastable Zr2Ni phase to vitrify with increasing f(R) was analyzed with a concept of communal entropy in the free volume theory with solid- and liquid-like cells proposed by Cohen and Crest. The MD-PCM for the metastable Zr2Ni phase suggests that Zr-based bulk metallic glass (BMG) can be regarded as an alloy in a high rotation entropy state of clusters and that glass transition takes place by percolation of the nuclei of a liquid-like glassy phase.

We have studied the local atomic arrangements of a Zr0.60Al0.15Ni0.25 bulk metallic glass (BMG) with molecular dynamics (MD) simulations based on a plastic crystal model (PCM). We have utilized features of orientationally disordered state of a molecule in plastic crystals. A Zr0.618Al0.146Ni0.236 alloy with an approximated composition to the Zr0.60Al0.15Ni0.25 has been created using MD-PCM from a Zr0.73Ni0.27 glassy alloy that possesses critically percolated Ni atoms. The MD-PCM dealt with icosahedral and tetrahedral clusters with 13 and five atoms, respectively, with a Ni, Al, or Zr atom at each center site of the clusters. After the Zr0.73Ni0.27 glassy alloy had been created with monatomic MD simulation by quenching from a liquid, the Zr and Ni atoms in the Zr0.73Ni0.27 glassy alloy were replaced with randomly oriented icosahedral and tetrahedral clusters, respectively. Subsequently, structural relaxation was performed after adjusting the density to that of the Zr0.618Al0.146Ni0.236 alloy. Total pair-distribution and interference functions revealed that the Zr0.618Al0.146Ni0.236 alloys created with MD-PCM exhibit the characteristics of a non-crystalline phase. Further, Voronoi polyhedra analysis revealed that the Ni-centered polyhedral clusters used as initial atomic arrangements for MD-PCM tend to reproduce the features of the conventional MD results. The origin of the excellent glass-forming ability of the Zr0.618Al0.146Ni0.236 alloy is attributed to the critically percolated cluster-packed structure.

The forming ability of amorphous and glassy alloys has been assessed with mixing enthalpy (ΔHmix) of a liquid phase based on Miedema's scheme. The ΔHmix's were calculated as a function of composition in an alloy for possible 2628 binary systems from 73 elements, and were approximated with interaction parameter Ω in a sub-regular solution model with coefficients Ωi (i = 0 to 3) for a cubic function of composition. The results revealed that 2627 systems were fitted by Ω′s within errors denoted by statistical adjusted R-square (R 2) ≥ 0.999, which includes R2 = 1 for 2409 systems. The values of Ωi for 1378 systems from 53 elements were selected and tabulated for assessing the forming ability of amorphous and glassy alloys. The analysis revealed that P and C in Fe-P and Fe-C binary alloys and simultaneous additions of Ni and Cu in La-, Zr-and Pd-based bulk metallic glasses exhibit a marked and peculiar composition dependence of ΔH mix. In a framework of Miedema's scheme, the most accurate values of ΔHmix for a liquid phase have been provided as a function of composition in an alloy system, which makes it possible to consider the forming ability of amorphous and glassy alloys deeply. © 2010 Elsevier Ltd. All rights reserved.

The glass transition temperature- (T(g)-) scaled Arrhenius plot (Angell plot) has been modified by considering viscosity (eta) of metallic glasses in a liquid and supercooled liquid state with absolute temperature (T). The log eta-(T(g)/T) relationships in Angell plot were modified as log eta-[(T(g)-T(0))/(T-T(0))] relationships where T(0) is the ideal glass transition temperature from Vogel-Fulcher-Tammann (VET) parameters. Introducing Delta T(g-0) ( T(g)-T(0)) makes it possible to regard the modified plot as Delta T(g-0)-scaled VFT plot. Using B from VFT parameters provides a relationship D(VFT)* = B/Delta T(g-0) similar to 38, in which T(g) was principally measured at a heating rate of 0.333 K s(-1). The analyses revealed that Delta T(g-0)-scaled VFT plot reflects alpha relaxation due to a motion of groups of atoms, and that Delta T(g-0)/(T(1)-T(0)) where T(1) is the liquidus temperature can be a glass-forming parameter. (C) 2009 Elsevier Ltd. All rights reserved.

The Zr60Al15(Ni,Cu)(25) noncrystalline alloys with their initial crystalline states from the ionic arrangements of a Fe3Al2Si3O12 garnet structure were created with molecular dynamics simulations based on a plastic crystal model (MD-PCM). The analyses with pair-distribution function revealed that the randomly-rotated octahedral clusters around the Cu sites or tetrahedral clusters around the Ni sites and subsequent annealing with MD-PCM make the Zr60Al15(Ni,Cu)(25) crystalline alloys to vitrify. The interference function indicated that the Zr60Al15Ni25 noncrystalline alloy created through rotating operation for the octahedral clusters gives the best fit with the experimental data in an as-quenched state. Crystallographic analyses indicated that the prototype of the garnet structure, Weaire-Phelan (A15) structure, gives inhomogeneous Wigner-Seitz cell for the solute elements and an optimized heat of mixing for atomic pairs in the Zr60Al15(Ni,Cu)(25) noncrystalline alloys. These crystallographic features due to Weaire-Phelan structure are a reason for the Zr60Al15(Ni,Cu)(25) alloys to have high glass-forming ability. (C) 2009 Elsevier Ltd. All rights reserved.

Molecular dynamics (MD) simulations based on a plastic crystal model (PCM) were performed for a Pd(0.4)Ni(0.4)P(0.2) alloy in Metal-Metalloid (M-MLD) type of bulk metallic glass (BMG). Two kinds of clusters of cubeoctahedron capped with four half-octahedra and trigonal prism were used as initial atomic arrangements of the Pd(0.4)Ni(0.4)P(0.2) alloy. Random rotations of clusters around their centers of gravity and subsequent structural relaxation vitrified the alloy. The high glass-forming ability of the Pd(0.4)Ni(0.4)P(0.2) alloy is due to the critically-percolated, cluster-packed structure that is a universal feature for both M-MLD and M-M types of BMGs.

Eighteen bulk metallic glasses (BMGs) with critical diameters over similar to 15 mm in Pd-, Zr-, Mg-, Y-, La-, Pt- and Ca-based multicomponent alloys were analyzed for their mole fractions of compositions with Golden Mean (phi similar to 1.618). The results proved that the 18 BMG compositions are describable with m phi(-n) or m phi(-n) where phi(-n) is phi(-(n+1)) plus phi(-(n-1)) and m and n are positive integers. The maximum difference in fractions between the analyzed and experimental compositions was 0.038. The irrational nature of (P makes the compositions of the 18 BMGs different from those of the stoichiometric intermetallic compounds and near eutectic compositions, leading to the high glass-forming ability. The possible prototypes of the 18 BMGs have the ability to form critically-percolated local atomic arrangements for both Metal-Metal and Metal-Metalloid types of BMGs. Golden Mean analysis provides a new alloy design for fractions of alloying elements owing to its irrationality. (C) 2009 Elsevier Ltd. All rights reserved.

The glass-forming ability (GFA) of binary metallic glasses was analyzed with data for the liquidus temperature (T(1)) acquired as a function of composition from binary phase diagrams, assisted by crystallographic data combined with amorphous-forming composition range (AFCR) and molecular dynamics (MD) simulations. A necessary condition for the formation of bulk metallic glasses (BMGs) was determined as Delta T(1) >= 300 K where Delta T(1) was defined as a decrease in T(1) due to eutectic reaction. The crystalline compounds with structure types of bcc or its derivative type, such as CsCl (B2), CrB (B(f)), Al(2)Cu (C16) and MoSi(2) (C11(b)), tended to be found in AFCR frequently. The total pair-distribution and interference functions revealed a high forming tendency of a noncrystalline Cu(10)Zr(7) structure created by MD. Simultaneous achievements of the Cu(10)Zr(7) structure for crystallographic features resulting from the bcc family structure and geometrical features in phase diagram for T(1) affect the formation of Cu(61.8)Zr(38.2) BMG. (C) 2008 Elsevier B.V. All rights reserved.

Molecular dynamics simulations based on plastic crystal model were performed for the Fe69.0Nb10.3B20.7 and Zr57.1Ni28.6Al14.3 alloys to investigate their forming ability and features of the noncrystalline structures. The Fe69.0Nb10.3B20.7 and Zr57.1Ni28.6Al14.3 alloys were created from C6Cr23 and Ti4Ni2O structures, respectively, by assuming the presence of hypothetical clusters in the crystalline structures under a treatment that the clusters and glue atoms are regarded as the components. The analysis with total pair-distribution function, g(r), revealed that these alloys have high tendencies to form noncrystalline structures while their partial g(r) profiles for pairs among components showed the presence of medium range order. Cluster packed structures from bcc derivative compounds cause high forming ability of noncrystalline structure and the medium range order in the noncrystalline structure.

The phase stabilities Of Cu2Mg and CuMg2 Compounds were analyzed for their noncrystallizations with molecular dynamics (MD) simulations based on the plastic crystal model (PCM), which includes a series of processes for random rotations of hypothetical clusters around their centers of mass, relaxation and annealing. The calculation results in terms of pair-distribution functions reveal that the Cu2Mg alloy created with PCIVI tends to form in a crystalline structure, whereas the CuMg2 alloy forms in a noncrystalline structure. MD simulations based on PCM are validated because they are consistent with the experimental results indicating that the compositions for the Cu2Mg and CuMg2 alloys are outside and inside the amorphous-forming composition range (AFCR), respectively PCM is of great importance due to its agreement with the experimental data on AFCR, which has yet to be obtained using conventional MD methods through quenching from a liquid phase. (C) 2008 Elsevier Ltd. All rights reserved.

Molecular dynamics simulations with a scheme to treat groups of atoms in an intermetallic compound as a hypothetical cluster were performed for Zr-Ni base alloys by allowing random orientations of the clusters that were imitated to plastic crystals in a class of soft matter. A binary Zr66.7Ni33.3 and ternary Zr66.7Al11.1Ni22.2 and Zr66.7Al22.2Ni11.1 alloys were analyzed for their local atomic arrangements and forming ability of a noncrystalline structure with total pair-distribution and interference functions and Voronoi polyhedra. The analysis revealed that a Zr66.7Al11.1Ni22.2 alloy created from the tetragonal Zr2Ni structure by replacing Ni with Al reproduces the features of the local atomic arrangements of the experimental data for a Zr60Al15Ni25 bulk metallic glass (BMG) in a supercooled liquid state while the alloy from the Zr6Al2Ni structure by substituting Al and Ni atoms agrees to the BMG in an as-quenched state. © 2008 Elsevier Ltd. All rights reserved.

A method to treat a part of atomic arrangements in a crystalline structure as hypothetical clusters was applied to analyze the similarity in local atomic arrangements between a noncrystalline structure and its corresponding crystalline structure. The molecular dynamics (MD) simulation revealed that a metastable cubic Zr2Ni crystalline structure transforms into a noncrystalline structure by permitting random cluster-rotations followed by annealing at a low temperature. The analyses for pair-distribution and interference functions exhibit a feature of noncrystalline structure, and qualitatively reproduce the features of experimental data. (C) 2008 Elsevier Ltd. All rights reserved.

The composition dependence of formation of ternary bulk metallic glasses (BMGs) has been analyzed with crystallographic data concerning 16873 ternary compounds with a composition triangle named L-M-S diagram for relative atomic size of constituent elements of L (Large), M (interMediate), and S (Small). As well as ternary compounds containing Cu(2) Mg, Fe(2)P and C(6)Cr(23) types, three types of ternary BMGs characterized by the relative atomic size of the main element of L- (La-, Zr-, Pd- and Ca-based BMGs), M- (Fe- and Mg-based BMGs) and S-types (Cu-based BMGs) are plotted in the L-M-S diagram. The L-M-S diagram with plots of all ternary compounds reveals a general tendency that the ternary compounds are frequently formed in the S-rich corner as compared to L- and M-rich corners. The L-M-S diagram shows that Fe(2)P and C(6)Cr(23) type compounds directly affect the formation of M-type BMGs and also possibly influence the formation of the L-type BMGs. The high glass-forming ability of La-, Zr- and Ca-based BMGs is due to features of their composition regions in the L-M-S diagram wherein ternary compounds infrequently appear and anti-Laves relationship to Cu(2)Mg type compounds holds in ternary systems.

A computational method to create a noncrystalline structure from a crystalline compound related, to metallic glass has been proposed based on the idea that groups of atoms in a compound can be treated as hypothetical clusters. This computational method was applied to the C6Cr23 Structure, which was viewed as an ensemble of clusters and remaining atoms in its a unit cell. Allowing the clusters to randomly rotate around their centers of mass caused drastic changes in the atomic arrangements from a crystalline to noncrystalline-like structure in the as-prepared structure. A subsequent relaxation in the molecular dynamics simulation confirmed the noncrystalline character of the atomic arrangements in the relaxed structure. (C) 2007 Elsevier Ltd. All rights reserved.

The glass forming ability of Gd-Co-Al ternary alloy systems with a composition ranging from 50% to 70% (molar fraction) for Gd and from 5% to 40% (molar fraction) for Al were investigated by copper mold casting and Gd60Co25Al15 bulk glass alloy cylinders with the maximum diameter of 5 mm were obtained. The reduced glass transformation temperature (T-g/T-m) and the distance of supercooling region Delta T-x are 0.616 and 45 K, respectively for this Gd-Co-Al alloy. The compressive fracture strength (sigma(f)) and elastic modulus (E) of Gd-Co-Al glassy alloys are 1 170-1 380 MPa and 59-70 GPa, respectively. The Gd-Al-Co bulk glassy alloys with high glass forming ability and good mechanical proper-ties are promising for the future development as a new type function materials.

A series of Gd-Ni-Al ternary glassy alloys with the maximum diameter of 4 mm were obtained by common copper mold casting. The maximum values of the reduce glass transformation temperature (T (g)/T (m)) and the distance of supercooling region Delta T (x) of these alloys in this study were 0.648 and 50 K, respectively. The compressive fracture strength (sigma (f)) and Young's modulus (E) of Gd-Ni-Al glassy alloys were 1,240-1,330 MPa and 63-67 GPa, respectively. The magnetic properties of these BMGs were investigated. The Gd-Ni-Al bulk glassy alloys with great glass forming ability and good mechanical properties are promising for the future development as a new type of function materials.

Gd65Fe20Al15, Gd65Fe15Al20 and Gd70Fe15Al15 bulk amorphous alloys were produced by copper mold casting method with the maximum diameters of 2, 1 and 1 mm, respectively. The crystallization temperature (T-x) and melting temperature (T-m) of the Gd65Fe20Al15 bulk amorphous alloy are 808 and 943 K, respectively. Accordingly, the temperature interval of T-m and T-x, Delta T-m (=T-m - T-x), is as small as 135 K and the reduced crystallization temperature (T-x/T-m) is as high as 0.86. The small Delta T-m and high T-x/T-m values are presumed to be the origin for the achievement of the high amorphous-forming ability of the Gd-Fe-Al bulk amorphous alloy. The Gd65Fe20Al15, Gd65Fe15Al20 and Gd65Fe15Al15 bulk amorphous cylinders with a diameter of I mm exhibit superparamagnetism at room temperature, while the amorphous ribbon shows the paramagnetism at room temperature. Finally, the mechanical properties of Gd65Fe20Al15 bulk amorphous alloys are investigated. (c) 2006 Elsevier B.V All rights reserved.

The formation of bulk metallic glasses (BMGs) has been analyzed with a tetrahedron composition diagram, which is comprised of constituent classes from blocks of elements in the periodic table. When Al and Ga are involved in the BMG composition environment. they are assumed to correspond to either s- or p-block elements. The analysis under the assumption reveals the presence of a composition band that connects the composition regions over different classes of BMGs. The diagram has a topological simplicity, is applicable to any multicomponent alloy system, and can be analyzed from the bonding nature of the atomic pairs. Thus, this diagram is an important tool for analyzing and developing BMGs.

A linear differential equation for the analyses of glass transition phenomena has been proposed by taking into account the delay effect due to the change in transportation of atoms near the glass transition temperature (T-g). Under the condition maintaining the order of the differential equation as the second, the non-linear differential equation proposed by Van Den Beukel and Sietsma is modified to obtain the analytic solution for a linear equation by introducing the following points: the delay effect which is described with a term of Mackey-Glass model, a concept of effective free volume (x(fe)(eff)) and its concentration expression (C-fe(eff)) which correspond to the equilibrium, and an additional term associated with C-fe(eff). In analyzing the linear equation, Doyle's p-function was used for the integral of reaction rate with respect to temperature (T). It is found that the linear equation proposed in the present study can describe the changes in free volume (x) with increasing temperature in the dx/dT - T chart, the sharp increase in free volume at T-g, and over shooting phenomena of free volume slightly above the T-g, as experimentally in thermal analyses for metallic glasses. The linear solution obtained in the present study is of great importance for the analyses of the glass transition because the change in free volume with increasing temperature on heating is described with fundamental functions. (C) 2006 Elsevier B.V. All rights reserved.

The glass forming ability of Gd-Co-Al and Gd-Al-Ni ternary alloy systems with a composition range of 50-70 at.% Gd and 0-40 at.% Al were investigated by copper mold casting. Bulk glassy alloys with composition of Gd60Co25Al15 and Gd60Ni15Al25 with the maximum diameters of 5 and 4 mm, respectively, were produced in the Gd-Al-Co and Gd-Al-Ni alloy systems The reduce glass transformation temperature (T-g/T-1) and the distance of supercooling region Delta T-x are 0.6 and 45 K for the Gd60Co25Al15 and Gd60Ni15Al25 bulk metallic glasses, respectively. The compressive fracture strength sigma(f) and Young's modulus E of these two glassy alloys are 1250 MPa and 63 GPa for Gd60Co25Al15, 1300 MPa and 65 GPa for Gd60Ni15Al25 alloy, respectively. The Gd-Co-Al and Gd-Al-Ni bulk glassy alloys with high glass forming ability and good mechanical properties are promising for the future development as a new type function materials. (C) 2006 Elsevier B.V. All rights reserved.

The glass transition in of Pd82Si18, Pd40Ni40P20 (number indicated at.%) and Pd40Cu30Ni10P20 metallic glasses has been analysed by carrying out numerical calculations to a linear differential equation, which relates to a non-linear differential equation proposed by Beukel and Sietsma. The linear solutions are obtained from the non-linear differential equation based on free volume theory by taking into consideration a function form Mackey-Glass model and a concept of effective equilibrium free volume, the latter of which is introduced to account for the lack of atomic transportation near glass-transition temperature (Tg). The calculation results to the linear solutions were plotted in free volume (x)-temperature (T) and dx/dT-T diagrams, and compared with those by Beukel and Sietma model. It is found that the calculation results of the linear solutions reproduces those of the Beukel and Sietma model with respects to the values of dx/dT in dx/dT-T diagram: sharp increasing at around Tg and overshooting slightly higher than Tg. In addition, the changes in free volume on heating are interpreted with chemical reactions in order to account for the implication of the linear model by introducing a concept of effective equilibrium free volume. © 2006 Elsevier B.V. All rights reserved.

The relationships of optimal compositions of bulk metallic glasses (BMGs) have been analyzed with a set of thermodynamic quantities of mismatch entropy normalized with respect to Boltzmann's constant (S-sigma/k(B)) and mixing enthalpy (Delta H-mix) and with assistance of classification result of BMGs. The analysis shows clear dependence of the location of S-sigma/k(B) and Delta H-mix. values for optimal compositions of ternary BMGs in S-sigma/k(B)-Delta H-mix chart in each alloy system. The ternary BMGs are summarized into four types: (1) Cu-based, (2) La-, Zr- and Ca-based, (3) Pd-based and (4) Fe- and Mg-based BMGs according to their maximum value of S-sigma/k(B) ((S-sigma/k(B))(max))and the largest and negative value of Delta H-mix ((Delta H-mix)(L.N.)) or their half values which are obtained for each system. These types of BMGs are related with the local arrangements of BMGs, which are widely accepted as an icosahedral structure for Metal-Metal type, a transformed tetragonal dodecahedrons and triacontrahedrons structure for Pd-Metalloid type, and a network-like structure for Metal-Metalloid type.

Bulk amorphous alloys with hard magnetic properties were produced by a copper mold casting method for Fe(45)Nd(45)A(10), Fe45Nd40Al15 and Fe42.5Nd42.5Al15 alloys in a cylindrical form with diameters of 3, 3 and 4 mm, respectively. The crystallization temperature (T-x) and melting temperature (T-m) of the Fe42.5Nd42.5Al15 bulk amorphous alloy are 813 and 877 K, respectively. Accordingly, the temperature interval between T-m and T-x, Delta T-m (=T-m-T-x), is as small as 64 K and the reduced crystallization temperature (T-x/T-m) is as high as 0.93. The small Delta T-m and high T-x/T-m values are presumed to be the origin for the achievement of the high amorphous-forming ability of the Fe-Nd-Al alloy. The Fe(45)Nd(45)A(10), Fe45Nd40Al15 and Fe42.5Nd42.5Al15 bulk amorphous cylinders with a diameter of 1 mm exhibit hard magnetic properties of 0.212-0.248 T for magnetization, 0.124-0.171T for remanence and 156-245kA/m for intrinsic coercive field at room temperature, The hard magnetic properties for these bulk amorphous alloys tend to transform to the soft type with decreasing diameter of the cylindrical samples. These Fe-Nd-Al bulk amorphous alloys with hard magnetic properties and high amorphous-forming ability are promising for future progress as a new type of Fe-based magnetic material.

Characteristics of atomic pairs in ferrous bulk metallic glasses (BMGs) have statistically been analyzed using digitized data on mixing enthalpy (Delta H (mix)({AB})) based on the Miedema's model and local atomic arrangements for binary compounds listed in Pettifor map. The main element of the ternary ferrous BMGs tend to be the element with intermediate atomic radius in a system, which is different from most of the other BMGs. The ternary ferrous BMGs exhibits strict restrictions with respect to Delta H (mix)({AB})'s for the formation of ferrous BMGs. These tendency and JAB restrictions are the necessity of multicomponent alloying for the formation of ferrous BMGs. The local atomic arrangements of BMGs were carried out for pseudo-binary systems in multicomponent BMGs by referring to the corresponding compositions in Pettiffor map with ratios of elements of 1:1, 2:1, 3:1, 4:3, 3:2 and 5:3. The analyses with respects to types of environment, coordination number, coordination notation and coordination symbol for binary compounds reveal the local atomic arrangements of BMGs containing a part of icosahedral clusters as a common basic atomic arrangements. This kind of statistical analyses using computers is useful for the further development of BMGs.

Iron-rich Fe50Nd50-xAlx (x = 5, 10, 15, 20 at%) alloys were produced by copper mold casting and melt-spinning in order to examine the formation of amorphous alloys. The bulk amorphous cylinders with diameters up to 1.5 mm have been obtained for the Fe50Nd35Al15 alloy. The crystallization temperature (T-x) and melting temperature (T-m) of the alloy are 774 and 880 K, respectively. Accordingly, the temperature interval of T-m, and T-x, Delta T-m (=T-m-T-x), is calculated to be 106 K, and the reduced crystallization temperature (T-x/T-m) is 0.88. The small Delta T-m and high T-x/T-m, values are presumed to be the origin for the achievement of the high amorphous-forming ability of the Fe-Nd-Al alloy. The bulk amorphous cylinder exhibits semi-hard magnetic properties at room temperature. i.e., 0.117 T for remanence and 50 kA/m for intrinsic coercive field for Fe50Nd35Al15 alloy with a diameter of 1.5 mm. Moreover, soft to hard magnetic transition between the ribbon and bulk specimens was observed in the Fe-rich Fe-Nd-Al alloys. The semi-hard magnetic properties for the Fe-rich Fe-Nd-Al amorphous alloys with high amorphous-forming ability are promising for future progress as a new type of Fe-based magnetic material.

Bulk metallic glasses (BMGs) have been classified according to the atomic size difference. heat of mixing (Delta H-mix) and period of the constituent elements in the periodic table. The BMGs discovered to date are classified into seven groups on the basis of a previous result by Inoue. The seven groups are as follows: (G-I) ETM/Ln-LTM/BM-Al/Ga, (G-II) ETM/Ln-LTM/BM-Metalloid (G-III) Al/Ga-LTM/BM-Metalloid, (G-IV) IIA-ETM/Ln-LTM/BM, (G-V) LTM/BM-Metalloid, (G-VI) ETM/Ln-LTM/BM and (G-VII) IIA-LTM/BM. where ETM. Ln, LTM, BM and IIA refer to early transition, lantlianide, late transition, group IIIB-IVB and group IIA-group metals, respectively. The main alloying element of ternary G-I, G-V and G-VII, ternary G-II and G-IV, and tertiary G-VI BMGs is the largest, intermediate and smallest atomic radius compared to the other alloying elements, respectively. The main alloying element of tertiary BMGs belonging to G-I. G-V. G-VI and G-VII is an element in the atomic pair with the largest and negative value of Delta H-mix (<(Delta H)under bar >(mix)(LN)). while the main element of ternary BMGs belonging to G-II and G-IV is independent of the atomic pair with <(Delta H)under bar >(mix)(LN). The characteristics of the main element derived for the ternary BMGs are directly applicable to multicomponent BMGs belonging to G-I. G-II, G-IV (Mg-based BMGs), G-V and G-VII. The main element can be the larger-sized element in the atomic pair with <(Delta H)under bar >(mix)(LN) or in the same group as the other elements for multicomponent BMGs belonging to G-III. G-IV (Be-containing Zr-based BMG) and G-VI. The main element of BMGs belonging to G-VI tends to change from the element with the smallest atomic radius in a ternary system to an element with a relatively large atomic size in a in multicomponent system. The change is due to an increase in glass-forming ability through multicomponent alloying of BMGs belonging to G-VI. The results of the classification of BMGs obtained in the present study are important for further development of BMGs, with the results providing a road map for the development of new BMG compositions.

Calculation methods for deriving the optimal alloy systems and compositions for the formation of bulk metallic glasses (BMGs) have been proposed by referring to the criteria for the achievement of high glass-forming ability which is proposed by Inoue et al. in the early 1990s. By using the Miedema's model, 2123 ternary systems are found to satisfy the criteria simultaneously, the rate of which is 3.4 % of the statistical population of 62196 ternary systems. The mismatch entropy normalized by Boltzmann constant (S-sigma/k(B)) and mixing enthalpy (Delta H-chem), which correspond to the criteria in terms of effects of atomic size differences and the heat of mixing, are calculated for the ternary amorphous alloys. The values of S-sigma/k(B) and Delta H-chem of the typical BMGs tend to be plotted densely in the S-sigma/k(B)-Delta H-chem chart. This tendency is of great importance for deriving the compositions of BMGs.

The calculation models in which the viscosity is used as a main parameter are proposed for the estimation of the three glass-forming ability (GFA) factors: critical cooling rate (R-c) for formation of glassy phase, reduced glass transition temperature (T-g/T-m) and supercooled liquid range (DeltaT(x) equivalent to T-x - T-g), where T-g, T-m and T-x are the glass transition, melting and crystallization temperature, respectively. The R-c and T-g/T-m were analyzed on the basis of the homogeneous nucleation and growth theory by the construction of a time-transformation diagram for the crystallization of metallic glass. On the other hand, DeltaT(x) was calculated on the basis of a free volume theory proposed by Beukel and Sietsma, and then was related with R-c calculated from the time-transformation curve. The calculations were carried out for Fe-, Pd-, Pt-, Zr-, Mg-based metallic glasses for which the viscosity is expressed by Vogel-Fulcher-Tammann equation or the Doolittle equation. The calculated results summarized in R-c - T-g/T-m and R-c - DeltaT(x) diagrams agree with the experimental data qualitatively. It was shown that all the GFA factors of metallic glasses can be calculated from viscosity. These results indicate that the viscosity is the key parameter for the determinations of R-c, T-g/T-m and DeltaT(x). (C) 2003 Elsevier B.V. All rights reserved.

Magnetic properties of (Nd, Pr)60-70Fe30-20Al10 amorphous alloys were studied for bulk specimens prepared by arc-melting. The bulk specimens with thicknesses ranging from 100μm to 6mm were prepared as fragments, which were obtained by crashing a mother alloy followed by arc melting. The bulk specimens exhibit an amorphous state up to 6mm for Nd60Fe30Al10, 3mm for Nd70Fe20Al10, 6mm for Pr60Fe30Al10 and 1mm for Nd70Fe20Al10. Bulk specimens with thicknesses ranging from 100μm to 6mm exhibit hard magnetism with coercive force (iHc) ranging from 100 to 300kA/m. The iHc of the bulk specimens tends to decrease with decreasing thickness. It is estimated that the soft to hard magnetic transition takes place approximately 100μm for (Nd, Pr)70Fe20Al10 amorphous alloys. The critical cooling rate for the formation of amorphous phase is estimated as less than 100K/s for (Nd, Pr)60-70Fe30-20 Al10 alloys from the analyses using thermodynamic quantities. © 2003 Elsevier B.V.

Thermodynamic and kinetic simulations were performed to clarify the formations of amorphous and nanocrystalline alloys On the basis of the Miedema's model partially assisted by a database, the amorphous-forming composition region (AFCR) and crystallization temperature (T-x) of the multicomponent amorphous alloys were calculated from thermodynamic approaches. On the other hand, kinetic simulations were performed for Ni-Nb binary eutectic system by the phase field model. The AFCRs calculated for ternary alloy systems containing practically important elements such as Al, Cu, Fe, Ni, Ti agree with the experimental trends. The values of T-x for iron-group-based alloys are calculated with approximate errors of several tens of Kelvin to the experimental data. For Ni62.4Nb37.6 alloy, the critical cooling rate (R-c) for formation of amorphous phase and incubation time (tau) for crystallization are calculated to be R-c= 3 x 10(2) K/s and tau=1000 s. These values are closed to the value calculated from the time-transformation diagram for crystallization based on the homogeneous nucleation theory (R-c=1.4 x 10(3) K/s tau=10(5) s). The present study indicates the importance of the simultaneous analyses of transformations from thermodynamic and kinetic aspects for the development of amorphous alloys in near future.

The effect of the structural disorder on the magnetic properties of Nd9-xFexAl10 (x = 20-60) melt-spun ribbons is investigated in the temperature range 4-300 K, as a function of both the composition and the thickness of the samples. The microstructure consists of very small Fe-Nd magnetic clusters randomly distributed within the amorphous matrix, whose size approaches a single magnetic domain. (C) 2004 Elsevier B.V. All rights reserved.

Since the recognition of stabilization phenomenon of supercooled liquid in multi-component metallic alloys without metalloid elements in 1988, a number of nonequilibrium alloys in a bulk form have been fabricated with the aim of clarifying the origin for its novel phenomenon and finding useful characteristics. This review deals with alloy systems in which the stabilization can be achieved, stabilization mechanism, and physical, chemical, mechanical and magnetic properties of the resulting glassy and nonequilibrium crystalline bulk alloys.

Ni-Fe-W alloys were produced by electrodeposition from an ammoniacal citrate bath having nickel sulphate, ferric sulphate and sodium tungstate as sources of nickel, iron and tungsten, respectively. The alloys prepared at low current densities have nanocrystalline structure, while those prepared at high current densities are amorphous. X-ray diffraction results show that the structure changes gradually from nanocrystalline to amorphous phase with an increase of current density. As the current density increases, tungsten content increases while iron content decreases. The hardness of the alloys increases with increasing tungsten content. The best mechanical properties among all the alloys are obtained for 51Ni-29Fe-20W alloy prepared at 600 A/m(2). Effect of sodium hypophosphite on the composition of the alloys produced at 2000 A/m(2) Was also studied. Addition of hypophosphite causes a decrease in tungsten content of the alloys. Further increase in the hypophosphite content causes a decrease of both iron and tungsten contents and an increase of phosphorus and nickel contents. For the alloys deposited from solutions containing sodium hypophosphite more than 0.03 mol/L, the total molar content of tungsten and phosphorus remains constant at 20 at%.

The composition, structure and magnetic properties of high cobalt-containing Co-Ni-P alloys have been examined by controlling electrodepostion parameters. The alloys were deposited at 323 K from an electroplating solution consisting of nickel and cobalt chlorides and sodium hypophosphite. The current density and pH of the solution were controlled to determine the conditions of forming amorphous films. The alloys prepared at a current density of 150 A/m(2) and pH of 5.20 include both amorphous and crystalline phases. The increase of pH to above 5.20 results in the formation of amorphous alloys without crystalline phase. The conditions of 220A/m(2) for current density and 5.24 for pH were optimum to prepare the amorphous alloy at the highest deposition rate of 5.19 x 10(-5) kg/m(2)/s. These amorphous alloys exhibited high saturation magnetization up to 1.3 T with coercivity of about 20 kA/m.

Amorphous and nanocrystalline Ni-W-P alloy films have been prepared by electrodeposition. The effect of sodium hypophosphite in the bath is important in determining the W and P contents of the alloy. The alloys prepared in the bath containing more than about 0.15 mol/L of sodium hypophosphite are only Ni-P alloys containing high P contents (> 21% (at)) and no W at all. However, as the sodium hypophosphite content is decreased, the W content in the alloy increases and reaches about 20% (at) with decreasing P content to about 1% (at) at 6 x 10(-4) mol/L of sodium hypophosphite. The alloys containing high P contents are amorphous, while those containing high W contents have a nanocrystalline phase with apparent grain size of 2.3 nm at 20% (at) W content. These nanocrystalline alloys show high hardness values up to about 780 MVH.

We have reviewed our recent results on high functional materials by utilization of subnanoscale ordered atomic configurations which can develop in glassy and crystalline bcc, hcp and fcc phases consisting of special elements. The glassy phase in Zr-based alloys consists mainly of subnanocale icosahedral ordered atomic configurations including high density of interface and exhibits unique mechanical properties which cannot be obtained for conventional crystalline alloys. The Ti-based bcc alloys with nanograin sizes of about 5 nm are formed in alloy systems including atomic pairs with positive heats of mixing and exhibit the similar mechanical properties as those for bulk glassy alloys. The Mg-Zn-Y hcp solid solutions can have a novel long-periodic hexagonal structure through stabilization caused by atomic level segregation of Y and Zn elements and the long periodic structure has enabled us to obtain a nanogranular hcp solid solution exhibiting high strength and good ductility. The Al-Fe fee solid solution in a sheet form is also formed by vapor evaporation and exhibits high strength and good ductility. The high strength is mainly attributed to the solid solution strengthening caused by the development of atomic scale Al-Fe ordered atomic configuration. The novel concept of developing new functional materials by the control of subnanoscale ordered atomic configurations is useful and its extension is expected to fabricate more variety of functional materials.

A synthesized calculation model for developing metallic glasses has been created by taking into account criteria for the achievement of high glass-forming ability (GFA) and viscosity. The model deals with amorphous-forming composition region (AFCR), crystallization temperature (T) and three GFA factors: critical cooling rate (R-c), reduced glass-transition temperature (T-g/T-m) and supercooled liquid region (DeltaT(x)=T-x-T-g) where T-g and T-m are glass transition and melting. temperature, respectively. The principle of the model is based on thermodynamic functions for multicomponent systems, i.e., mismatch entropy and mixing enthalpy which express the criteria in terms of the number of elements, atomic size differences and the heat of mixing. By combining these thermodynamic quantities with the Miedema's semi-empirical model, AFCR was calculated, and was compared with the experimental results. The GFA factors were also analyzed from viscosity. The R, was derived from transformation diagram of metallic glasses for crystallization while AT, was calculated by solving a differential equation expressing the change in free volume with temperature. As a result of these analyses, R-c-T-g/T-m and R-DeltaT(x) diagrams were found to fit with the experimental results qualitatively. Furthermore, crystallization temperature (T.) was also calculated for multicomponent metallic glasses by the modification of the Miedema's binary model for the calculation of T. The reduced crystallization temperature (T-x/T-l), where T-l is liquidus temperature, was calculated for evaluating GFA of metallic glasses instead of T-g/T-m. Some of the calculation methods used in the present study have the advantage giving results as a function of composition; thus, there exists possibility to lead to the prediction of glassy alloys compositions. In this sense, the present calculation methods are completely different to the current method for the development of new metallic glasses relying on the empirical criteria which suggest only appropriate systems and/or elements of the alloys for the achievement of high GFA. In near future, this kind of calculation technique can be used for the prediction of optimal compositions of the metallic glasses with high GFA.

A model for calculating crystallization temperature (T-x) of multicomponent metallic glasses is proposed by modifying the Miedema's model which is used for calculating T-x of binary systems. The calculations were carried out for nearly 900 metallic glasses including 470 binary and 398 ternary alloys. In the present model, the cavity formation energy (DeltaH(cavity)(for)) for multicomponent metallic glasses was theoretically derived on the basis of the Miedema's model. The equation for expressing the relation between experimental T-x and theoretical DeltaH(cavity)(for) was statistically analyzed by the least-squares method, yielding T-x = 4.16 x statistically analyzed by the least-squares method, yielding T-x = 4.16 x DeltaH(cavity)(for) + 318. The binary and ternary systems tend to show different equations between T-x and 6 DeltaH(cavity)(for). The inherent equation in each system was analyzed as simultaneous achievement of the increase in stability of metallic glasses and decrease in DeltaH(cavity)(for) due to multicomponent alloying. Furthermore, the glass-forming ability was predicted by reduced crystallization temperature instead of reduced glass transition temperature. As a result, it was found that reduced crystallization temperature can be calculated close to reduced glass transition temperature except for Pt, Pd- and La-based systems. It is of great importance that T-x can be calculated for multicomponent metallic glasses by semi-empirical method.

Bulk Nd60Fe30Al10-xBx (x = 0, 2.5, 5, 7.5 and 10 at%) alloys with hard magnetic properties were prepared by an arc melting method. The bulk alloys have weights of 10 and 100 mg with button shapes of I and 6 mm in thickness, respectively. The X-ray diffraction and TEM observation data reveal that the Nd60Fe30Al10 bulk alloy exhibits an amorphous phase while the other alloys consist of partial crystalline and amorphous phases. The bulk Nd60Fe30Al10 amorphous alloy of I mm in thickness exhibits crystallization temperature (T-x) of 802 K, eutectic temperature (T-e) of 925 K, and reduced crystallization temperature (T-x/T-e) of 0.87. The alloy exhibits hard magnetic properties at 298 K, i.e., saturation magnetization of 0.13 T, remanance of 0.09 T, and intrinsic coercive filed of 275 kA/m under an applied field of 1242 kA/m. These thermal and magnetic properties are nearly the same as those for the corresponding bulk amorphous cylinders of 1 to 12 mm in diameter prepared by copper mold casting. The replacement of Al with B in Nd-Fe-Al amorphous alloy causes a decrease in amorphous-forming ability (AFA), although their hard magnetic properties remain almost unchanged. The reason for the decrease in AFA was analyzed using mixing enthalpy (DeltaH(mix)) and mismatch entropy (S-sigma) corresponding the empirical criteria for the achievement of high AFA. Furthermore, amorphous-forming composition regions (AFCRs) were calculated by giving a limitation for formation of an amorphous phase to DeltaH(mix) and S-sigma values, which arises from the statistics for 6500 amorphous alloys listed in a database. The calculated AFCR of the Nd-Fe-Al and Nd-Fe-B alloy systems agrees with the experimental data reported previously. The decrease in AFA by the replacement of Al with B in the Nd60Fe30Al10-xBx alloys is interpreted from the result that Nd60Fe30B10 is located near the edge of the AFCR in Nd-Fe-B system.

The supercooled liquid range (DeltaT,) was calculated on the basis of the free volume theory proposed by Beukel and Sietsma. A differential equation which expresses the change in free volume from a non-equilibrium to an equilibrium state has been analyzed numerically for Ni, metallic glasses and SiO2 systems. The Vogel-Fulcher-Tammann (VFT) equation for viscosity was used to define the equilibrium free volume. The maximum AT(x) was calculated as 56K for the SiO2 system. The calculated DeltaT(x) was approximately six times smaller than the experimental result. The calculation results of the log R-c (Rc: critical cooling rate for glass formation)-DeltaT(x) diagram shows a tendency similar to the experimental result; log Rc decreases linearly with increasing DeltaT(x). An approximate solution of the differential equation was also obtained with elementary functions. It was found that the glass transition temperature (T-g) and DeltaT(x) can be obtained schematically in the free-volume-temperature diagram. All the factors expressing the glass-forming ability of the metallic glasses can be derived from the VFT parameters.

This paper deals with our recent results on the reduced instability of metallic supercooled liquid and the resulting bulk glassy alloys by paying attention to the following factors; alloy compositions, glass-forming ability, less unstable mechanism, computed simulations of glass-forming ability and glass formation range, atomic configurations and production techniques. As demonstrated in this review, the high reduced instability of metallic supercooled liquid has already opened up new basic science and engineering application fields and its importance is expected to increase more and more hereafter.

An equation expressing the transformation curve for crystallization of metallic glasses has been proposed by using two parameters, viscosity and melting temperature (T-m). The Vogel-Fulcher-Tammann (VFT) equation, eta = eta (0)exp(B/(T - T-0)) where eta (0), B and T-0 (ideal glass transition temperature) are empirical parameters. was used for expressing the viscosity, A Time-reduced Temperature-Transformation (T-T-r-T) diagram was calculated using the following five quantities: reduced temperature (T-r = T/T-m) three reduced viscosity parameters (eta (0) = eta (0)/T-m, B-r = B/T-m and T-0r = T-0/T-m), and reduced critical cooling rate (R-cr = R-c/T-m) for formation of the glassy phase, The R-ct in the T-T-r-T diagram was calculated for Ni, metallic glasses and SiO2. The glass-forming ability (GFA) was estimated from T-0r - R-ct (R-c = R-c/T-m) diagrams corresponding to T-g/T-m - R-c diagrams obtained experimentally. The metallic glasses with T-0r of 0.55 are calculated to have R-cr ranging from 10(-5) to 10(0) s(-1), which agrees with the experimental data that metallic glasses with T-g/T-m of 0.6 or more have R-c of less than 10(3) K/s. The following three point, are clarified: (1) the higher GFA of metallic glass is achieved because of higher viscosity. (2) higher viscosity causes both the homogeneous nucleation frequency (l(v)(hom)) and the ratio (l(N)/l(max)), at reduced now. temperature against the maximum of l(v)(hom), to decrease, and (3) the R-cr is numerically derived from reduced viscosity parameters.

Ge-based amorphous alloys produced by rapid solidification of the melt usually contain Al as one of the important alloying elements for improving their glass-forming ability. In the present paper we discuss the formation of two Ge-based amorphous alloys in Ge-Ni-La and Ge-Li-Ca systems, where Ge is alloyed with heavy Ni, La and light Li, Ca elements. The structure and crystallization behavior of the Ge-Ni-La alloy were extensively studied by transmission electron microscopy (TEM) including high-resolution imaging, differential scanning calorimetry (DSC) and X-ray diffractometry. The nature of phase transformations is discussed on the basis of isothermal and continuous heating data analyses as well as the results of in situ X-ray diffraction (XRD) studies during heating. (C) 2001 Elsevier Science B.V. All rights reserved.

The amorphous-forming composition range (AFCR) was calculated for 338 ternary amorphous alloy systems on the basis of the database given by Miedema's model in order to examine the applicability of the model, to analyze the stability of the amorphous phase, and to determine the dominant factors influencing the ability to form an amorphous phase. The mixing enthalpies of amorphous and solid solution phases were expressed as a function of alloy compositions on the basis of chemical enthalpy. Based on the Eshelby and Friedel model, an elastic enthalpy term was added to the model for the solid solution. Furthermore, an average melting temperature of the constituent elements was added to the model as the topological enthalpy in an amorphous phase. An amorphous phase was assumed to have been formed at the composition where the enthalpy of an amorphous phase was smaller than that of a solid solution. The AFCR was calculated for 335 systems except for the Al-Cu-Fe, Al-Mo-Si and Au-Ge-Si systems. The calculated results are in agreement with the experimental data for Cu-Ni- and Al-Ti-based systems. For typical amorphous alloy systems exemplified by the Zr-, La-, Fe- and Mg-based systems, it was recognized that the calculated AFCR had been overestimated as a result of the model being simplified. We have also shown that the elastic enthalpy term arising in a solid solution phase stabilizes the amorphous phase, and the stabilization mechanism is particularly notable in Mg-based amorphous alloy systems. Short-range order plays an important role in the formation of Al-, Fe- and Pd-metalloid based systems. The following factors have a great influence on amorphous-forming ability: (1) three empirical rules for the achievement of high AFA, (2) melting temperature and viscosity at the melting temperature, (3) elastic enthalpy arising in a solid solution, and (4) short-range order observed in an amorphous phase. The importance of the latter two factors was only identified as a result of the present study.

Evaluation of critical cooling rate R-c for lass formation was carried out quantitatively for metallic glasses. A fundamental equation proposed for oxide glasses was modified fur metallic glasses. In the calculation both Gibbs free energy of the molten alloys and the effect of the differences in atomic size were taken into account. The calculation was carried out for three groups: pure metals, typical glass-forming systems, and the latest metallic glasses with a large glass-forming ability found after 1990. The calculated results were in agreement with previous data. As examples, the R-c for Ni metal. Co- and Pd-Gu-based metallic glasses in the present work were 9.1 x 10(8), 1.2 x 10(5) and 1.6 x 10(-2) K/s, respectively, instead of 3 x 10(10), 3.5 x 10(5) and 1 x 10(-1) K/s in the previous work. The following points are clarified: (1) T-m(2)/eta characterizes R-c as is typical for the Pd-Cu-based metallic glass with a low melting point as well as high viscosity at the melting point; (2) negative heats of mixing and atomic size mismatch above about 1 12% affect the reduction of R-c from 10(-2) to 10(-7) and from 10(-1) to 10(-2): and (3) the reduction of R-c is understood as a stabilization of liquid state. (C) 2001 Elsevier Science B.V. All rights reserved.

Extensive magnetic studies on Nd90-xFexAl10 (x = 35 similar to 50) amorphous alloys in the shape of both melt-spun ribbons with thicknesses between 25 and 150 mum and rods with diameters no larger than 3 mm prepared by mould casting and suction casting indicate a complex magnetic behaviour depending on the Fe content. The microstructure and magnetic properties are strongly dependent on the cooling rate and the preparation technique. The high values of the coercive field of Nd90-xFexAl10 amorphous samples in the as-cast state as well as their increase by the decrease of the cooling rate and temperature result from the formation of very small metastable or non-equilibrium clusters, whose size vary as a function of the quench rate. The presence of these magnetic clusters is evidenced by multiphase magnetic transitions observed from the ac-susceptibility measurements at low temperatures.

Ge68Cr14Al10Ce4Sm4 amorphous alloy was found to have a multistage crystallization behaviour. First stage of crystallization has been studied by differential scanning calorimetry, X-ray diffraction and transmission electron microscopy including high-resolution imaging. This phase transformation can not be described just by one of the following mechanisms: polymorphous, eutectic, primary and spinodal decomposition and is rather a combination of the polymorphous and primary crystallization. An activation energy E (an energy barrier opposing a reaction) obtained using Kissinger analysis from the shift of the peak temperature in the DSC curve was 360 kJ/mol. Crystalline structure of an unknown phase formed under heating was studied. (C) 2000 Kluwer Academic Publishers.

Chemical mixing enthalpy (DeltaH(Chem)) and mismatch entropy normalized by Boltzmann constant (S-sigma/k(B)) corresponding to the three empirical rules for the achievement of high amorphous-forming ability (AFA) were calculated with thermodynamical functions for the gross number of 6450 alloys in 351 ternary amorphous systems. The ternary amorphous alloys have DeltaH(chem) Of -86 to 25 kJ/mol and S-sigma/k(B) of 1.8 x 10(-3) to 5.7. The average values of DeltaH(chem) and S-sigma/k(B) are calculated to be -33 J/mol and 0.33, respectively. The 30 alloys in 9 ternary amorphous systems including 10 alloys in Ag-Cu-Fe system have positive values of DeltaH(chem). Most of the ternary amorphous alloys have the values of DeltaH(chem) and S-sigma/k(B) inside a trapezoid region in DeltaH(chem) - log(S-sigma/k(B)) chart except mainly for the H- and the C-containing alloys, Si-W-Zr system and the 32 alleys having positive values of DeltaH(chem). The analysis of AFA was carried out for typical five ternary amorphous systems. The following four results are derived. 1)Al-La-Ni and B-Fe-Zr alloys have high AFA in accordance with the concept of the three empirical rules. 2) The further multiplication of alloy components causes an increase in the AFA of Al-B-Fe alloys. 3) Thermodynamical factors represented by melting temperature and viscosity at the melting temperature are required for evaluation of AFA for Mg- and Pd-based amorphous alloys. 4) A tendency for log(S-sigma/k(B)) to increase with decreasing DeltaH(chem) is recognized in each alloys system, implying the stabilization of an amorphous phase against solid solution and intermediate phase.

The Nd50Fe40Si10 amorphous ribbons with thicknesses up to 80 mu m prepared by melt-spinning method exhibit good hard magnetic properties at room temperature. The improvement of the hard magnetic properties was obtained by increasing the thickness of the amorphous ribbons or by applying proper thermal treatments. The hard magnetic properties of the Nd50Fe40Si10 amorphous alloy are related to the existence of the ferromagnetic clusters in the amorphous matrix.