L1_2-Ni_3(Al,Cr)沉淀先期效应的微观相场模拟

Computer Simulation of the Early Stage of Precipitation of L1_2-Ni_3(Al,Cr) Using Microscopic Phase-Field Method

基于微观相场模型,研究Ni80Al7Cr13合金在873K时效过程中L12结构Ni3(Al,Cr)的沉淀先期效应。分析沉淀早期微结构、成分及有序度随时间的变化。研究发现,原子有序化早于原子簇聚,首先形成有序度很低的L10结构非化学计量比有序畴,随着时间的延长,有序畴的有序度逐渐提高,当有序度增大到一定时,L10结构非化学计量比有序畴逐渐向非化学计量比L12结构转变,最后非化学计量比L12结构有序畴的成分和有序度随时间的增长逐渐达到化学计量比L12结构的成分和有序度,在化学计量比L12结构的有序相中,Al原子倾向于占据αⅠ反位,而Cr原子则倾向于在αⅡ反位择优占位。

Based on the microscopic phase-field model, the evolution of atom morphology of Ni80Al7Cr13 ternary alloy is simulated at 873 K during the aging process. The early stage effect of precipitation is studied and discussed through analysising the changes of microstructure, composition and order parameter with the time. The study shows that the ordering of atom is happened earlier than the clustering of atom in the early time of precipitation, firstly forming the nonstoicheometric Llo ordered domain with very low order parameter, then the order parameter increasing with the increase of the aging time. At the same time, the ordered domain expands toward the nonordered domain, and the nonstoicheometric Llo ordered domain gradually transforms to the nonstoicheometric L12 structure when the order parameter of Llo increases to some degree. At last, the composition and the order parameter of nonstoicheometric L12 ordered domain attain to that of the stoicheometric L12 ordered domain. In the stoicheometric L12 ordered domain.Al priority occupies the 1α antisite, Cr priority occupies the αⅡ antisite.