Seeded growth of Ti-46Al-8Nb polysynthetically twinned crystals with an ultra-high elongation  

作　　者：Hao Jin Qing Jia Quangang Xian Ronghua Liu Yuyou Cui Dongsheng Xu Rui Yang 

机构地区：[1]Institute of Metal Research,Chinese Academy of Sciences,Shenyang,110016,China [2]University of Chinese Academy of Sciences,Beijing,100049,China

出　　处：《Journal of Materials Science & Technology》2020年第19期190-195,共6页材料科学技术（英文版）

基　　金：National Natural Science Foundation of China(No.51701209);National Key Research and Development Program of China(Nos.2016YFB0701304)。

摘　　要：Large size polysynthetically twinned crystals of Ti-46 Al-8 Nb alloy with a parallel lamellar microstructure were successfully prepared using a Ti-43 Al-3 Si seed by our new operation.A large amount of columnar B2 phase paralleling to the growth direction was found in the final lamellar microstructure.Higher growth rate(>30 mm/h)led to the failure of seeding process.Based on these results,a new mechanism is proposed to describe the seeding process of the hypo-peritectic Ti Al alloys.The peritecticαphase is suggested to directly nucleate from the melt,and then act as nucleus for transformedαphase in the subsequentβtoαtransformation.At the higher growth rate,the appearance ofβphase secondary dendrites and homogeneous nucleation lead to the failure of seeding process.High Nb addition leads to a large amount of residualβphase,and theseβdendrites finally evolve into B2 phase.The room temperature tensile elongation was measured to be 11.9-18.5%for Ti-46 Al-8 Nb PST crystals,which is the highest ever reported value for Ti Al based alloys.

关 键 词：TiAl alloys Polysynthetically twinned crystals Peritectic solidification Seeded growth DUCTILITY 

分 类 号：TG146.23[一般工业技术—材料科学与工程]