Globularization Mechanism and Near Isotropic Properties in Subcritical Heat‑Treated Ti6Al4V Fabricated by Directed Energy Deposition  

作　　者：Guohao Zhang Zhiwei Hao Meng Wang Xufei Lu Zhuang Zhao Qian Wang Xin Lin Jing Chen Weidong Huang 

机构地区：[1]State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi’an 710072,China [2]MIIT Key Laboratory of Metal High Performance Additive Manufacturing and Innovative Design,Northwestern Polytechnical University,Xi’an 710072,China [3]International Center for Numerical Methods in Engineering,Universidad Politecnica de Cataluna,08034 Barcelona,Spain [4]Institute of Machinery Manufacturing Technology,China Academy of Engineering Physics,Mianyang 621054,China

出　　处：《Acta Metallurgica Sinica(English Letters)》2023年第6期937-948,共12页金属学报（英文版）

基　　金：This work was financially supported by the National Natural Science Foundation of China(No.52275381);the Nation Defense Basic Scientific Research Program of China(No.JCKY2017204A021);the Shaanxi Province double chain fusion project(No.2021LLRH-08).

摘　　要：Microstructure with globularαphase is desirable as it contributes to preferable comprehensive mechanical properties for titanium alloys.However,titanium alloys fabricated by directed energy deposition(DED)are mainly characterized by the lamellarαphase within the basket-weave microstructure,which often leads to severe anisotropy and inferior low cycle fatigue(LCF)properties.To address this,the subcritical annealing and the cyclic annealing were applied to DED Ti–6Al–4V in order to achieve the transformation from the lamellarαphase to the globularαphase.The microstructural characteristics and the globularization behavior ofαphase during heat treatment were investigated.The results show that the aspect ratio ofαis significantly decreased with the subcritical annealing due to the coarsening of lamellarα.Furthermore,the globularαis obtained with the cyclic annealing as a combination result of the termination dissolution and the side surface growth of the lamellarα.These contribute to a pronounced reduction of 85.4%in the ductility anisotropy,compared with the as-built specimens,and superior comprehensive mechanical properties including LCF are achieved with the formation of globularα.

关 键 词：Directed energy deposition TI-6AL-4V Subcritical heat treatment COARSENING Globularization 

分 类 号：TB333[一般工业技术—材料科学与工程]