Surface-color Regulation Under Ambient Condition And Mechanical-Property Regulation Under High Pressure Of Metallic Glasses

Metallic glasses are thermodynamically non-equilibrium and kinetically metastable materials,meaning their structure and properties vary over time.Metallic glasses,for example,will undergo structural relaxation during thermal annealing,moving from an amorphous state with higher energy and lower stability to an amorphous state with lower energy and higher stability,and eventually to a crystalline form with the lowest energy and highest stability.Embrittlement is inescapable during the structural relaxation process,which has an impact on the use of metallic glasses as structural materials.In this subject of how the structure-property relationship changes through time,this thesis addresses it by examining the aging effect of Ce-based metallic glass under natural settings and the mechanical performance of Zr-based metallic glass after high pressure in two different investigations.What factors influence the oxidation rate of Ce-based metallic glass in natural conditions? This is a scientific question linked to the aging effect of Ce-based metallic glass.Temperature,the glass-transition temperature,oxide-film integrity,surface smoothness,Pilling-Bedworth ratio,structural flaws,surface scratches,and chemical segregation are among the physical characteristics and structural aspects addressed.Using composition modulation,a new series of metallic glasses have been invented which can automatically have and change colors at ambient conditions.The physical mechanism of this coloration is mainly based on the inflection of light.Surface color can be controlled by adjusting the atomic percentage of impurity elements.The diversity in local oxidation rates is reflected in the color contrast.This surface-color contrast has been linked to surface or interior structural flaws,as well as chemical segregation.Based on the notion of surface-color contrast,a new approach of identifying surface defects is developed.Why is the plasticity of the embrittled annealed metallic glass regained after highpressure treatment? This is a scientific question linked to the improvement of mechanical characteristics of Zr-based metallic glass after high-pressure treatment.The annealing-induced embrittlement of metallic glasses limits their use as structural materials.This study uses a high-pressure treatment at room temperature to restore the plastic strain of annealed metallic glass to that of as-cast,so resolving the embrittlement problem.The current thesis evaluates the changes in enthalpy,density,and entropy of specimens after annealing and high-pressure treatment,and indicates that the plasticity recovery is due to high-pressure generated structural disordering,or an entropyrejuvenation physical process.The following is a summary of the research findings:(1)Inventing a new type of metallic glasses that can change colors automatically in natural condition.(2)Developing a new surface detecting technique based on natural color contrast.(3)Developing a new high-pressure treatment technique that solves annealing-induced embrittlement and uncovers a physical mechanism of entropy rejuvenation.It is believed that these findings will make future scientific research and industrial applications of metallic glasses easier.