The liquid metal embrittlement(LME)of advanced high-strength steels caused by zinc(Zn)has become a critical issue hindering their widespread application in the automotive industry.In this study,atomic-scale simulation...The liquid metal embrittlement(LME)of advanced high-strength steels caused by zinc(Zn)has become a critical issue hindering their widespread application in the automotive industry.In this study,atomic-scale simulations are carried out to elucidate the underlying cause of this phenomenon,namely grain boundary embrittlement due to Zn segregation at iron(Fe)grain boundaries.A machine learning moment tensor interatomic potential for the Fe-Zn binary system is developed,based on which the thermodynamics of grain boundary segregation is evaluated.The yielded segregation energy spectrum of Zn in BCC Fe reveals the quantitative relationship between the average segregation concentration of Zn at Fe grain boundaries and the macroscopic Zn content,temperature,and fraction of grain boundary atoms.It suggests a strong thermodynamic driving force for Zn segregation at the Fe grain boundaries,which correlates directly with the grain boundary energy:high-energy grain boundaries can accommodate a large amount of Zn atoms,while low-energy grain boundaries exhibit a certain degree of repulsion to Zn.Kinetically,Zn enters the grain boundaries more easily through diffusion than by penetration.Nonetheless,the grain boundary embrittlement caused by Zn penetration is more severe than that by Zn diffusion.The embrittlement effect generally increases linearly with the increase in Zn concentration at the grain boundary.Altogether,it suggests that the LME in steels induced by grain boundary segregation of Zn emerges as a combined consequence of Zn melt penetration and solid-state diffusion of Zn atoms.展开更多
Solidification structure variation of single phase alloy with undercooling prior to nucleation has been widely studied. The progress, especially during the last decade, is reviewed so as to give a comprehensive knowle...Solidification structure variation of single phase alloy with undercooling prior to nucleation has been widely studied. The progress, especially during the last decade, is reviewed so as to give a comprehensive knowledge for it, in which the emphases are laid on the structure evolution mechanism and the potential application. Lastly, the future interesting subjects are presented.展开更多
Zr55Al10Cu30Ni5 bulk metallic glass was rolled up to 95% in thickness reduction at room temperature, and the dependences of microstructure and thermal stability on the strain were investigated. It is revealed that pha...Zr55Al10Cu30Ni5 bulk metallic glass was rolled up to 95% in thickness reduction at room temperature, and the dependences of microstructure and thermal stability on the strain were investigated. It is revealed that phase transformations do not occur during the rolling, but the split of the crystallization peaks becomes more and more obvious with increasing thickness reduction. Analyses of the radial distribution functions and the pair correlation functions indicate that the rolling has enhanced the short-range order, which should be responsible for the enlarging split of the crystallization peaks.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52071204)Natural Science Foundation of Shanghai Municipal(No.22ZR1428700)SJTU Kunpeng&Ascend Center of Excellence,and MaGIC of Shanghai Jiao Tong University.
文摘The liquid metal embrittlement(LME)of advanced high-strength steels caused by zinc(Zn)has become a critical issue hindering their widespread application in the automotive industry.In this study,atomic-scale simulations are carried out to elucidate the underlying cause of this phenomenon,namely grain boundary embrittlement due to Zn segregation at iron(Fe)grain boundaries.A machine learning moment tensor interatomic potential for the Fe-Zn binary system is developed,based on which the thermodynamics of grain boundary segregation is evaluated.The yielded segregation energy spectrum of Zn in BCC Fe reveals the quantitative relationship between the average segregation concentration of Zn at Fe grain boundaries and the macroscopic Zn content,temperature,and fraction of grain boundary atoms.It suggests a strong thermodynamic driving force for Zn segregation at the Fe grain boundaries,which correlates directly with the grain boundary energy:high-energy grain boundaries can accommodate a large amount of Zn atoms,while low-energy grain boundaries exhibit a certain degree of repulsion to Zn.Kinetically,Zn enters the grain boundaries more easily through diffusion than by penetration.Nonetheless,the grain boundary embrittlement caused by Zn penetration is more severe than that by Zn diffusion.The embrittlement effect generally increases linearly with the increase in Zn concentration at the grain boundary.Altogether,it suggests that the LME in steels induced by grain boundary segregation of Zn emerges as a combined consequence of Zn melt penetration and solid-state diffusion of Zn atoms.
基金This work was supported by the National Natural Science Foundation of China under grant No. 50171043 and the Open Foundation from State Key Laboratory of Solidification Process-ing.
文摘Solidification structure variation of single phase alloy with undercooling prior to nucleation has been widely studied. The progress, especially during the last decade, is reviewed so as to give a comprehensive knowledge for it, in which the emphases are laid on the structure evolution mechanism and the potential application. Lastly, the future interesting subjects are presented.
基金supported by the National Natural Science Foundation of China (Grant No. 50671066)
文摘Zr55Al10Cu30Ni5 bulk metallic glass was rolled up to 95% in thickness reduction at room temperature, and the dependences of microstructure and thermal stability on the strain were investigated. It is revealed that phase transformations do not occur during the rolling, but the split of the crystallization peaks becomes more and more obvious with increasing thickness reduction. Analyses of the radial distribution functions and the pair correlation functions indicate that the rolling has enhanced the short-range order, which should be responsible for the enlarging split of the crystallization peaks.
