Research on the Microstructure and Deformation Mechanism of TC4Titanium Alloy Welded Joints Based on In Situ Observations

Author of the article:SHAO Jiajun1, JIA Runchen1, LI Qian2, ZHANG Siyuan2, XIN Shewei2, ZENG Weidong1

Author's Workplace：1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China; 2. NorthwestInstitute for Nonferrous Metal Research，Xi'an 710016, China

Key Words：TC4; tungsten inert gas; microstructure; in situ tensile

Abstract：The microstructure evolution and mechanical behavior of a TC4 titanium alloy following tungsten inert gaswelding were systematically investigated. The influence of the temperature gradient and preferred orientation on the growthof columnar crystals in the weld zone was revealed through EBSD scanning and metallographic examination.Reconstruction analysis of the heat-affected zone (HAZ) indicates that the prior β grains generally exhibit a typical <100>texture orientation. During cooling, the lamellar α phase precipitated from the β grains shows almost no distinct variantselection, demonstrating characteristics of crystallographic inheritance. A combination of in situ SEM tensile tests andfracture microscopy reveals that slip lines are predominantly distributed in the base metal zone and decrease in numbercloser to the weld, which is dominated by prismatic slip. Microcracks are found to nucleate primarily at grain boundariesduring deformation, indicating that grain boundaries play a critical role in plastic deformation and fracture evolution.