Microstructure and mechanical properties of Ti-6321 titanium alloy joint by tungsten inert gas welding

Abstract

High-quality thick Ti-6321 titanium alloy welded joints were obtained by tungsten inert gas（TIG）welding， the microstructure changes of fusion zone， heat affected zone and base metal zone of the welded joints before and after annealing were compared.The impact properties， fracture toughness and tensile properties were tested， and which were compared with the base metal. The results show that the microstructure of the fusion zone before annealing is composed of coarse β columnar grains with fully grown intragranular acicular martensite α′ phase， and heat affected zone consists of equiaxed structure with β matrix and primary α phase， martensite α′ phase precipitates in β matrix.After annealing， the martensite α′ phase in β matrix of the fusion zone and heat affected zone completely transforms into secondary α phase. The impact toughness， fracture toughness， tensile strength and elongation of Ti-6321 titanium alloy welded joints are 80.3 J/cm2， 113.00 MPa·m1/2， 873 MPa and 9%， respectively， which are 104.7%， 84.1%， 100% and 67.7% of the base metal，respectively. Compared with the fracture of the base metal， the impact fracture of welded joints has a coarser stepped surface and smaller equiaxed dimples， while the fracture surface of toughness is more flat and the fatigue crack propagation zone is narrower.

Keywords

• ti-6321 titanium alloy
• tig welding
• heat treatment
• microstructure
• mechanical property