Microstructure and mechanical properties of Ti6321 alloy welded joint by GTAW

Abstract

Titanium and its alloys have excellent combination of properties, such as low density, high specific strength and corrosion resistance, and they are extensively used in many industrial fields. This work is aiming at investigation on the microstructure and mechanical properties of Ti–6Al–3Nb–2Zr–1Mo (Ti6321) alloy joints by Gas Tungsten Arc Welding (GTAW) with filler materials. The results indicated that the microstructure of the fusion zone (FZ) is composed of acicular α, massive α, and Widmanstatten α+β. The heat affected zone (HAZ) near FZ consists of coarse and acicular α structures of grain boundary α, Widmanstatten α+β. The heat affected zone (HAZ) near base metal consists of primary α phase and transformed β containing acicular α. Microhardness values for HAZ are higher than that of FZ and base metal, and there are the peak values for the HAZ near the weld metal. The tensile strength of joint is almost equal to that of base metal, and the fracture locations of all the tensile specimens are in base metal, and it is well in accordance with the relationship between the content of strengthening and interstitial elements and microstructure and mechanical properties of welded joints. The tensile fracture morphology of joint presents obviously the characteristic of ductile fracture, which is related to the bigger and deeper dimples distributed on the surface of joint. The HAZ impact toughness is lower than that of the BM and FZ.