Study On The Relationship Between The Characteristic Temperatures And Composition Of Cu-based Metallic Glasses

The melt-spun Cu_55-xZr₄₅Al_x?x=6,7,9?and Cu_100-xZr_x?x=35.5,45,50?were investigated and their amorphous structure were comfirmed by X-ray diffraction?XRD?and high-resolution transmission electron microscopy?HR-TEM?.Non-isothermal and isothermal crystallization kinetics,VF temperature T₀ and Kauzmann T_k of metallic glasses were investigated using differential scanning calorimetry?DSC?.The Kissinger,Ozawa,Kissinger-Akahira-Sunose?KAS?,Flynn-Wall-Ozawa?FWO?,Arrhenius equations were utilized to obtain activation energies.Besides,the Vogel-Fulcher and Lasocka equations were used to determine VF temperature T₀ and Kauzmann T_k,respectively.The main research results of the work are as follows:?1?Variation laws of glass transition temperature T_g,the onset crystallization temperature Tx,the crystallization peak temperature Tp of metallic glasses Cu_55-xZr₄₅Al_x and Cu_100-xZr_x are obtained,finding that these three temperatures shift to higher temperature with the increasing heating rate.Meanwhile,changing rule of all characteristic temperatures?T_g,Tx,Tp?of ternary metallic glasses Cu_55-xZr₄₅Al_x and binary metallic glasses Cu_100-xZr_x with varying comosition are acquired,finding that characteristic temperatures of Cu_55-xZr₄₅Al_x increase with increasing Al atomic percentage;All characteristic temperatures?T_g,Tx,Tp?of binary metallic glasses Cu_100-xZr_x increase with decreasing Zr atomic percentage.?2?The activation energies of the glass transition and crystallization reaction Eg,Ex and Ep of ternary metallic glasses Cu_55-xZr₄₅Al_x and binary metallic glasses Cu_100-xZr_x were calculated by Kissinger and Ozawa equations.It is found that the calculated activation energies using Kissinger method are greater than the calculated activation energies using Ozawa method and their values are similar.The glass transition activation energies Eg of ternary metallic glasses Cu55-x Zr45 Alx and binary metallic glasses Cu_100-xZr_x are greater than the onset crystallizationactivation energies Ex.Besides,the relationship between the local activation energy E?determined by Kissinger-Akahira-Sunose?KAS?and Flynn-Wall-Ozawa?WFO?methods and the crystallized volume fraction ? were investigated in non-isothermal crystallization process.In addition,the relationship between the local activation energy E? obtained by Arrhenius equation and the crystallized volume fraction ? of isothermal crystallization process was analysed in Cu₅₀Zr₅₀ and Cu₅₅Zr₄₅ metallic glasses.?3?Each isothermal DSC curve exhibits a single exothermic crystallization peak after a incubation period in Cu₅₅Zr₄₅ and Cu₅₀Zr₅₀ metallic amorphous.It can be seen that incubation time increases with decreasing annealing temperature,which suggests that the atoms are of slower mobility at lower annealing temperature,which is disadvantage to crystallization.?4?The relationship between the crystallized volume fraction ? and temperature T during non-isothermal crystallization process at various heating rates shows a sigmoid type with temperature in Cu_55-xZr₄₅Al_x and Cu_100-xZr_x metallic glass.This sigmoid type is divided into three stages and the scope of three stages are basically the same in Cu-based binary and ternary metallic glasses.In other words,the scope of three stages are not affected by heating rates,crystallization temperatures,compositions in binary or ternary metallic glasses.The relationship between the crystallized volume fraction ? and annealing time t at different annealing temperatures show are also basically the same,which suggests that the scope of three stages are not affected by annealing temperatures,compositions in binary or ternary metallic glasses.Besides,the steepness of the curve reduce with increasing annealing temperature.?5?The fitting VF temperature T₀ is 630.4 K,649.4 K,665.4 K in Cu₄₉Zr₄₅Al₆,Cu48Zr45Al7 and Cu46Zr45Al9 metallic amorphous,respectively,and 651.4 K,658.9 K,690.37 K in Cu₅₀Zr₅₀,Cu₅₅Zr₄₅ and Cu64.5Zr35.5 metallic amorphous,respectively.In addition,changing rule T₀ of ternary metallic glasses Cu_55-xZr₄₅Al_x and binary metallic glasses Cu_100-xZr_x with varying comosition are acquired,finding that T₀ of Cu_55-xZr₄₅Al_x increases with increasing Al atomic percentage and T_g to T₀ ratio ranges from 1.08-1.12;T₀ of binary metallic glasses Cu_100-xZr_x increases with decreasing Zr atomic percentage and T_g to T₀ ratio ranges from 1.05-1.06.?6?The Kauzmann temperature T_k is 626.1K,639.5K,654.4K in Cu₄₉Zr₄₅Al₆,Cu48Zr45Al7 and Cu46Zr45Al9 metallic amorphous,respectively,and 645.2 K,653.6 K,674.8 K in Cu₅₀Zr₅₀,Cu₅₅Zr₄₅ and Cu64.5Zr35.5 metallic amorphous,respectively.In addition,changing rule T_k of ternary metallic glasses Cu_55-xZr₄₅Al_x and binary metallic glasses Cu_100-xZr_x with varying comosition are acquired,finding that T_k of Cu_55-xZr₄₅Al_x increases with increasing Al atomic percentage and T_g to T_k ratio ranges from 1.10-1.13;T_k of binary metallic glasses Cu_100-xZr_x increases with decreasing Zr atomic percentage and T_g to T_k ratio ranges from 1.06-1.07.Besides,VF temperatures T₀ and Kauzmann temperatures T_k approximately equal in size,namely,T₀?T_k.?7?Thermodynamical and kinetic ideal glass transition temperature,namely,Kauzmann temperature T_k and Vogel-Fulcher temperature T₀ have a linear relationship with glass transition temperature T_g,relationship of which can be expressed as T_k=1.085T_g-121.08 and T₀=0.84T_g-40.04 in different metallic glasses,respectively.