Prediction Of Viscosities Of Bulk Metallic Glass Systems And The Study On Their Correlation With Glass-forming Ability

Metallic glasses have drawn extensive attention and research in recent years due to their excellent mechanical,physical and chemical properties.The formation of metallic glass is mainly affected by kinetics and thermodynamics.Viscosity is an important kinetic factor that has great influence on the formation of metallic glass.Lack of viscosity data makes it difficult to study its correlation with glass-forming ability.Based on this,a new model was proposed in this work to predict the viscosity of metallic glass,and glass-forming ability was discussed.Mainly carried out the following work:A new CALPHAD(CALculation of PHAse Diagram)-based viscosity model was established.For the Au-Ag-Cu system,the viscosity data of pure elements,sub-binary systems and ternary system in the literature were evaluated and optimized,and the database for the viscosity was established via CALPHAD-based viscosity model.CALPHAD-based viscosity model is valid and suitable for predicting the viscosities of the Au-Ag-Cu based alloys.For the Zr-Cu-Al bulk metallic glass system,the viscosity data of pure elements,sub-binary systems and ternary system in the literature were evaluated and optimized,and the database for the viscosity was established via CALPHAD-based viscosity model.CALPHAD-based model is valid and suitable for predicting viscosities of bulk metallic glass systems.The viscosity database was utilized to construct the viscosity surface in the full composition of the Zr-Cu-Al ternary system.For the Zr-Cu-Al-Y bulk metallic glass system,the viscosity data of pure elements and six boundary binary systems were evaluated and optimized.Combined with the viscosity parameters of six boundary binary systems and Zr-Cu-Al boundary ternary system,an accurate and reliable description of the viscosity of Zr-Cu-Al-Y quaternary system was established by optimization via CALPHAD-based viscosity model.The viscosity parameters of Zr-Cu-Al-Y quaternary system also were obtained.CALPHAD-based viscosity model is valid and suitable for optimizing and calculating the viscosity of bulk metallic glass quaternary system.Viscosity projection surface in the full composition of the Zr-Cu-Al ternary system at the liquidus temperature was constructed by using the established database,and the correlation between viscosity and glass-forming ability was studied.It is found that viscosity is not the only factor affecting the glass-forming ability.The mismatch entropy and driving force factors should be considered.