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<p>TIG welding melds together two disparate alloys, Ti–6Al–4V (ASTM Grade 5) and CP-Ti (ASTM Grade 2), by subjecting them to intense heat. Subsequent to this fusion, a sequence of heat treatments ensues, encompassing uniform annealing of the solid solution, quenching, and aging at diverse temperatures. The welded section undergoes meticulous scrutiny via optical and electron microscopes to scrutinize the modifications and development of the microstructure. These alterations, swayed by the processing temperature, profoundly influence the conversion of the <i>α</i> + <i>β</i> two-phase region at the weld boundary and the heat-affected zone. Ultimately, these modifications govern the mechanical attributes of the weld. In addition to microstructural analysis, hardness testing and tensile evaluation were conducted to correlate the observed transformations with the resulting mechanical performance. Variations in thermal cycles led to distinct morphologies, including the formation of acicular <i>α</i>′ martensite in rapidly quenched samples and coarsened <i>α</i> laths in slowly cooled conditions. Such morphological differences directly affect strength, ductility, and residual stress distribution across the welded joint. The role of post-weld heat treatment proved critical in stabilizing the microstructure, reducing internal stresses, and enhancing weld toughness. Particular attention was directed towards the heat-affected zone, where heterogeneous transformations occurred due to the temperature gradient imposed by welding. The dissolution of the β phase at elevated temperatures and its subsequent transformation upon cooling contributed to notable microstructural heterogeneity. This heterogeneity was reflected in the measured mechanical properties, as regions with refined <i>α</i> + <i>β</i> lamellae displayed higher hardness and strength, whereas areas with coarser morphologies exhibited reduced mechanical resistance. Overall, the study demonstrates that careful control of welding parameters and subsequent heat treatments is essential for tailoring the microstructure and, consequently, optimizing the mechanical behavior of dissimilar titanium alloy joints. The findings contribute valuable insights into the metallurgical phenomena governing TIG-welded titanium alloys and provide practical guidelines for improving joint performance in aerospace, biomedical, and high-performance engineering applications.</p>

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Influence of Heat Treatment on the Microstructure of TIG Welding Between Ti–6Al–4V and Ti–CP

  • 期刊论文

  • 发表日期：

    2025年10月7日

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  • Manh Thang Sai,
  • Tien Dung Nguyen,
  • Anh Xuan Nguyen,
  • Viet Quyen Vu,
  • Duong Nam Nguyen,
  • Mai Khanh Pham

摘要

TIG welding melds together two disparate alloys, Ti–6Al–4V (ASTM Grade 5) and CP-Ti (ASTM Grade 2), by subjecting them to intense heat. Subsequent to this fusion, a sequence of heat treatments ensues, encompassing uniform annealing of the solid solution, quenching, and aging at diverse temperatures. The welded section undergoes meticulous scrutiny via optical and electron microscopes to scrutinize the modifications and development of the microstructure. These alterations, swayed by the processing temperature, profoundly influence the conversion of the α + β two-phase region at the weld boundary and the heat-affected zone. Ultimately, these modifications govern the mechanical attributes of the weld. In addition to microstructural analysis, hardness testing and tensile evaluation were conducted to correlate the observed transformations with the resulting mechanical performance. Variations in thermal cycles led to distinct morphologies, including the formation of acicular α′ martensite in rapidly quenched samples and coarsened α laths in slowly cooled conditions. Such morphological differences directly affect strength, ductility, and residual stress distribution across the welded joint. The role of post-weld heat treatment proved critical in stabilizing the microstructure, reducing internal stresses, and enhancing weld toughness. Particular attention was directed towards the heat-affected zone, where heterogeneous transformations occurred due to the temperature gradient imposed by welding. The dissolution of the β phase at elevated temperatures and its subsequent transformation upon cooling contributed to notable microstructural heterogeneity. This heterogeneity was reflected in the measured mechanical properties, as regions with refined α + β lamellae displayed higher hardness and strength, whereas areas with coarser morphologies exhibited reduced mechanical resistance. Overall, the study demonstrates that careful control of welding parameters and subsequent heat treatments is essential for tailoring the microstructure and, consequently, optimizing the mechanical behavior of dissimilar titanium alloy joints. The findings contribute valuable insights into the metallurgical phenomena governing TIG-welded titanium alloys and provide practical guidelines for improving joint performance in aerospace, biomedical, and high-performance engineering applications.