Uncovering the hierarchical clusters in the heat-affected zone of an electron beam weldedα/βtitanium alloy joint  

作　　者：C.Xu X.H.Shao H.J.Yang M.Lv H.Q.Liu X.L.Ma 

机构地区：[1]Shenyang National Laboratory for Materials Science,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China [2]School of Materials Science and Engineering,University of Science and Technology of China,Shenyang 110016,China [3]Suzhou laboratory,Suzhou 215028,China [4]Department of Mechanical Engineering,Kyushu University,Fukuoka 819-0395,Japan [5]Bay Area Center for Electron Microscopy,Songshan Lake Materials Laboratory,Dongguan 523808,China

出　　处：《Journal of Materials Science & Technology》2024年第7期120-132,共13页材料科学技术（英文版）

基　　金：supported by the National Natural Science Foun-dation of China(Grant Nos.51871222 and 52171021);Japan Soci-ety for the Promotion of Science(No.P20737);Natural Science Foundation of Liaoning Province(No.2023-MS-018).

摘　　要：Using high-resolution transmission Kikuchi diffraction(TKD)and transmission electron microscopy(TEM),we examined the hierarchical clusters that form in situ in the heat-affected zone(HAZ),which are com-monly referred to as“ghost”structures,of bimodal titanium alloy Ti-5Al-2Sn-2Zr-4Mo-4Cr(wt%,TC17).The ghost structures are enriched with Al elements but poor in Mo and Cr compared to the surroundingβmatrix.TKD results show that the ghost structure in middle-HAZ mainly consists ofα_(L)laths with a high-angle grain boundary,which exhibits the classic Burgers orientation relationship(BOR)with the host matrix,while it encircles theα_(P)grains in far-HAZ.And the ghost structure is evidenced to form via in-complete martensitic transformation.TEM results further confirm that the ghost structure is composed ofαL and tinyβ_(L)laths with BOR,with the former being enriched with Al and poor with Cr and Mo,while the latter is the opposite.Interestingly,twoα_(L)variant clusters with a check-mark morphology are fre-quently observed viewed along[0001]_(αL)//[110]_(βL)directions,which are dominated by the crystallographic and geometrical relationships betweenαandβphases.Based on the microstructural characterization,it is hypothesized that the ghost structure is transformed from the initialα_(P)phase,due to the coupling ef-fect of high thermal stress(which induces the formation of a large number of dislocations)and element diffusion caused by sudden temperature increase and plunge cooling in the HAZ during the welding pro-cess.

关 键 词：TC17 titanium alloy Electron beam welding(EBW) The ghost structure Transmission Kikuchi diffraction(TKD) Transmission electron microscopy(TEM) 

分 类 号：TG146.23[一般工业技术—材料科学与工程]