Analysis of Optimal Compositions of Ternary Bulk Metallic Glasses with Thermodynamic Quantities

摘要

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_σ/k_b) and mixing enthalpy (ΔH_(mix)) and with assistance of classification result of BMGs. The analysis shows clear dependence of the location of S_σ/k_b and ΔH_(mix) values for optimal compositions of ternary BMGs in S_σ/k_b-ΔH_(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_σ/k_b ((S_σ/k_b)_(max)) and the largest and negative value of ΔH_(mix) ((ΔH_(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.