Ti_(3)Al合金凝固过程晶核形成及演变过程的模拟研究  

Simulation of nucleation and evolution process of nuclei during solidification of Ti_(3)Al alloy

作　　者：李昌 侯兆阳[1] 牛媛 高全华[1] 王真[1] 王晋国[1] 邹鹏飞 Li Chang;Hou Zhao-Yang;Niu Yuan;Gao Quan-Hua;Wang Zhen;Wang Jin-Guo;Zou Peng-Fei(School of Science,Chang’an University,Xi’an 710064,China)

机构地区：[1]长安大学理学院,西安710064

出　　处：《物理学报》2022年第1期181-190,共10页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:50831003)资助的课题。

摘　　要：采用分子动力学方法对Ti_(3)Al合金的形核机理进行了模拟研究,采用团簇类型指数法(CTIM),对凝固过程不同尺度的原子团簇结构进行了识别和表征,深入研究了临界晶核的形成和长大过程.结果表明,凝固过程体系包含了数万种不同类型的原子团簇结构,但其中22种团簇结构类型对结晶形核过程起关键性作用.在晶核的形成和长大过程,类二十面体(ICO)原子团簇、类BCC原子团簇和缺陷FCC及缺陷HCP原子团簇在3个特征温度点T_(1)(1110 K),T_(2)(1085 K)和T_(3)(1010 K)时达到数量上的饱和,并根据数量和空间分布随温度的变化,得到了它们在形核和长大过程相互竞争的关系.跟踪平行孪生晶粒形成和长大的过程发现,临界晶核是由FCC原子构成的单相结构,并未观察到亚稳BCC相优先形核的过程;平行孪生结构是由FCC单相晶核在沿密排面逐层生长过程中形成的.结果还表明,CTIM相比于其他微观结构表示方法,能更为准确地揭示凝固过程微观结构的转变特征.The nucleation mechanism of Ti_(3)Al alloy is simulated by the molecular dynamics method in this work.The atomic clusters on different spatial scales are identified in the solidification process by the cluster-type index method(CTIM),and the formation process and the growth process of critical nucleus are studied in depth.It is found that the solidification system contains ten thousands of different types of atomic cluster structures,but only 22 types play a key role in the nucleation process.In the nucleation and growth process of nuclei,the ICO-like cluster,the BCC-like cluster,and the defective FCC cluster and the defective HCP cluster respectively reach their saturation points at the characteristic temperature T_(1)(1110 K),T_(2)(1085 K)and T_(3)(1010 K).And the competition processes of these clusters are revealed according to the changes of their number and spatial distribution with temperature.By tracing the nucleation and growth process of the grain with parallel twin,it is found that the critical crystal nucleus is composed of single-phase FCC structures,and the preferent nucleation of metastable bcc structure is not observed.The twinned structure is formed by the layer-by-layer growth along the close-packed plane.It is also found that the CTIM is more accurate than other methods in revealing the microstructural characteristics during the solidification.

关 键 词：TIAL合金 形核机理 分子动力学模拟 原子团簇 

分 类 号：TG146.23[一般工业技术—材料科学与工程]