AUTHOR=Shao Ling , Zhang Xinyu , Chen Yingwei , Zhu Liu , Wu Sujun , Liu Qijie , Li Weiwei , Xue Na , Tu Zhibiao , Wang Tianle , Zhang Jitang , Dai Sheng , Shi Xinxing , Chen Mengliang 

TITLE=Why do cracks occur in the weld joint of Ti-22Al-25Nb alloy during post-weld heat treatment?

JOURNAL=Frontiers in Materials

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2023.1135407

DOI=10.3389/fmats.2023.1135407

ISSN=2296-8016

ABSTRACT=<p>Ultrasonic pulse frequency tungsten inert gas welding technology was adopted to join Ti-22Al-25Nb alloy. There were some cracks in the Ti-22Al-25Nb alloy weld joint after post-weld heat treatment. The hardness and Young’s modulus of α<sub>2</sub>, O, and <italic>β</italic>/B2 phases in Ti-22Al-25Nb alloy were examined with an <italic>in situ</italic> nanoindentation technique. The phase transition stresses of three different phases in the weld joint of Ti-22Al-25Nb alloy were analyzed to explain why cracks occur in the weld joint of Ti-22Al-25Nb alloy during post-weld heat treatment. The results show that mean hardness is highest for the α<sub>2</sub> phase, second-highest for the O phase, and lowest for the <italic>β</italic>/B2 phase; the mean Young’s modulus has the same trend in Ti-22Al-25Nb alloy. Phase transition stress results in cracks in the weld joint of Ti-22Al-25Nb alloy during post-weld heat treatment. By improving post-weld heat treatment, the ultimate strength of the Ti-22Al-25Nb alloy weld joints reaches 750 MPa, which is 72.5% that of the base material.</p>