Cu75Ni25合金平衡固-液界面的微观结构

Microstructure of Equilibrium Solid-liquid Interface of Cu75Ni25 Alloy

采用NPH系综分子动力学(molecular dynamics,MD)方法模拟了Cu75Ni25合金的平衡固-液界面,并对其界面结构及属性进行了深入探究。根据相图计算,取Cu75Ni25合金成分点,求得不同晶向的熔点,Tm,[100]=1508.31 K,Tm,[110]=1514.92 K,Tm,[111]=1523.35 K,熔点存在各向异性。在界面区,统计了平衡构型的数密度、序参数、Ni原子浓度以及质量密度的分布曲线,展示了固-液界面的diffuse nature;所有参数在由固相向液相衰减的过程中呈现出很好的双曲正切的连续变化规律,其中采用Ni原子浓度计算得到的界面宽度明显小于采用其他属性计算得到的界面宽度。此外,按照“10%~90%”规则,以序参数为标准计算得到的界面宽度同样存在非常一致的各向异性;采用序参数aq 6计算得到的界面宽度始终大于序参数ξ的界面宽度。

Microstructure of the equilibrium solid-liquid interface of Cu75Ni25 alloy was simulated by the NPH ensemble molecular dynamics(MD)method,and its interfacial structure and properties were thoroughly investigated.Based on the phase diagram obtained by research,the anisotropic melting points of different crystallographic orientations were obtained at Cu75Ni25 composition point:Tm,[100]=1508.31 K,Tm,[110]=1514.92 K,Tm,[111]=1523.35 K.Moreover,the distribution curves of number density,order parameters,Ni atomic concentration and mass density were also calculated in the interfacial zone,showing the diffuse nature of solid-liquid interface.Furthermore,all parameters exhibited hyperbolic tangent profiles during decaying from bulk solid to liquid,and the interfacial width calculated from Ni atomic concentration was obviously smaller than that calculated by other properties.According to the“10%to 90%”rule,the interfacial width calculated from the different order parameter also had very consistent anisotropy;All the interfacial widths calculated from aq 6 were larger those of the correspondingξ.