Temperature-gradient induced microstructure evolution in heat-affected zone of electron beam welded Ti-6Al-4V titanium alloy
来源期刊：JOURNAL OF MATERIALS SCIENCE TECHNOLOG2019年第8期
论文作者：Shilin Zhang Yingjie Ma Sensen Huang Sabry S.Youssef Min Qi Hao Wang Jianke Qiu Jiafeng Lei Rui Yang
文章页码：1681 - 1690
摘 要：The heat-affected zone（HAZ） of electron beam welded（EBW） joint normally undergoes a unique heat-treating process consisting of rapid temperature rising and dropping stages, resulting in temperature-gradient in HAZ as a function of the distance to fusion zone（FZ）. In the current work,microstructure, elements distribution and crystallographic orientation of three parts（near base material（BM） zone, mid-HAZ and near-FZ） in the HAZ of Ti-6Al-4V alloy were systematically investigated. The microstructure observation revealed that the microstructural variation from near-BM to near-FZ included the reduction of primary α（αp） grains, the increase of transformed β structure（βt） and the formation of various α structures. The rim-α, dendritic α and abnormal secondary α（αs） colonies formed in the mid-HAZ, while the "ghost" structures grew in the near-FZ respectively. The electron probe microanalyzer（EPMA） and electron back-scattered diffraction（EBSD） technologies were employed to evaluate the elements diffusion and texture evolution during the unique thermal process of welding. The formation of the various α structures in the HAZ were discussed based on the EPMA and EBSD results. Finally, the nanoindentation hardness of "ghost" structures was presented and compared with nearby βt regions.
Shilin Zhang1,2，Yingjie Ma1,2，Sensen Huang1,3，Sabry S.Youssef1,2，Min Qi1,2，Hao Wang1,2，Jianke Qiu1,2，Jiafeng Lei1,2，Rui Yang1,2
1. Institute of Metal Research,Chinese Academy of Sciences2. School of Materials Science and Engineering,University of Science and Technology of China3. School of Materials and Engineering & Key Laboratory for Anisotropy and Texture of Materials,Northeastern University
摘 要：The heat-affected zone（HAZ） of electron beam welded（EBW） joint normally undergoes a unique heat-treating process consisting of rapid temperature rising and dropping stages, resulting in temperature-gradient in HAZ as a function of the distance to fusion zone（FZ）. In the current work,microstructure, elements distribution and crystallographic orientation of three parts（near base material（BM） zone, mid-HAZ and near-FZ） in the HAZ of Ti-6Al-4V alloy were systematically investigated. The microstructure observation revealed that the microstructural variation from near-BM to near-FZ included the reduction of primary α（αp） grains, the increase of transformed β structure（βt） and the formation of various α structures. The rim-α, dendritic α and abnormal secondary α（αs） colonies formed in the mid-HAZ, while the "ghost" structures grew in the near-FZ respectively. The electron probe microanalyzer（EPMA） and electron back-scattered diffraction（EBSD） technologies were employed to evaluate the elements diffusion and texture evolution during the unique thermal process of welding. The formation of the various α structures in the HAZ were discussed based on the EPMA and EBSD results. Finally, the nanoindentation hardness of "ghost" structures was presented and compared with nearby βt regions.
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