近共晶成分Ni-P非晶合金微结构特征的原子模拟分析  

Atomistic Simulation for Local Atomic Structures of Amorphous Ni-P Alloys with Near-Eutectic Compositions

作　　者：彭超[1] 李媛 邓永和[1] 彭平[1] 

机构地区：[1]湖南大学材料科学与工程学院,长沙410082

出　　处：《金属学报》2017年第12期1659-1668,共10页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目Nos.51071065和51428101~~

摘　　要：采用分子动力学方法模拟了Ni_(100-x)P_x(x=19.0、19.4、19.6、19.8、20.0、21.0)合金在冷速为5×10^(12)K/s下的快速凝固过程,并采用Voronoi多面体指数<n_3,n_4,n_5,n_6>和团簇类型指数(Zn_i/(ijkl)_i…)对其局域原子结构进行了表征。结果发现,Ni原子的团簇属性主要是高配位(Z≥12)的Frank-Kasper团簇及其变形结构,典型的化学短程序为NiZ-2P3,基本团簇间可通过交叉共享(IS)联结形成中程序结构;而P原子的局域结构除了Z=10的BSAP多面体外,还存在大量高配位(特别是Z=12)的Frank-Kasper结构形态,典型的化学短程序为Ni_(12)P;并且,P芯基本团簇的壳层原子全部为Ni,其间只能通过顶点共享(VS)、边共享(ES)和面共享(FS)联结形成扩展团簇。BSAP多面体及其相关结构被证实对Ni_(100-x)P_x非晶合金的形成具有重要影响,其数量在共晶点x=19.6时最多,偏离共晶点越远,所占比例越小,其结果与不同浓度下Ni_(100-x)P_x合金非晶形成能力的变化趋势一致。这可能就是Ni-P合金在共晶点具有最强非晶形成能力的原因。Ni100-xPx alloys with near-eutectic compositions have a strong glass forming ability （GFA）, but the microstructure prototypes and their evolution in various solidification processes are still unclear now. To reveal their unique structures, a series of molecular dynamics simulations for the rapid solidification process of liquid Ni100-xPx（x=19.0, 19.4, 19.6, 19.8, 20.0, 21.0） alloys were performed at a cooling rate of 5× 10^12 K/s, and their local atomic configurations at 300 K were characterized by Voronoi polyhedron index （n3,n4,n5,n6 ）and cluster type index （Zn/（ijkl）1...）. The results show that the local atomic structures of Ni atoms are mainly Frank-Kasper clusters with high coordination （Z≥12） as well as their distorted configurations. Their chemical short-range orders are mostly Niz-2P3, and these basic clusters can be further aggregated into medium-range orders （MROs） by intercross-sharing （IS） linkages. The majority of P-centered clusters are bi-capped square Archimedean anti-prism （BSAP） polyhedrons, but lots of Frank- Kasper clusters with higher coordination exist in the amorphous Nil00-xPx alloys. Their typical chemical short-range orders are Ni12P. In these short range orders （SROs） centered by P, all shell atoms are found to be Ni atoms, and no MRO can be detected except for their extended clusters linked by vertex-sharing （VS）, edge-sharing （ES） and face-sharing （FS）. The BSAP polyhedrons and their correlative structures play a crucial role in the formation of amorphous Ni100-xPx alloy. Their quantity is demonstrated to have a significant impact on the glass transformation of rapidly solidified Ni100-xPx alloys. It is found that the number of BSAP polyhedrons and their deformed structures at eutectic composition point x=19.6 is the largest among Ni100-xPx alloys, and the farther x deviates from the eutectic composition point, the smaller the proportion of BSAP polyhedrons and their structures more related to all P-centered clusters, which ar

关 键 词：Ni-P非晶合金 分子动力学 BSAP结构 非晶形成能力 

分 类 号：TG139[一般工业技术—材料科学与工程]