Change of microstructure and properties of dual titanium alloy join interface in hot working history

Abstract

In order to get workpiece with high tensile stresses in bore region and high temperature duration, creep strength in outskirts, the dual alloy samples made of high temperature titanium alloy Ti60 and high strength titanium alloy Ti6246 had been joined by inertia friction welding(IFW). Then these samples were isothermal forged at 9400c and 9750c, and different heat treatment followed. Changes of microstructure and properties of dual titanium alloy join interface in hot working history were examined at this article. The results show equiaxed α structure varied into basketweave structureat at as-welded join interface, especially a character of widmannstaten structure emerged from Ti6246 alloy side heat effect region, after gradient heat treatment. Immersed ultrasonic testing prove deformation can availably eliminate weld defect through metal on two side of weld line deeper embedding each other. The results of properties test also show the join strength of dual titanium alloy through isothermal deformation and gradient heat treatment are better than that of as-welded samples. Tensile strength, yield strength, elongating rate, reduction in area of sample at 5500c also increase 51 to145 MPa, 37 to 101 MPa, 1.6% to 5.3%, 15.3% to 3.3% than that of as-welded samples respectively. The rupture life of Ti60/Ti6246 dual titanium samples with join interface can sustain to go beyond 100 hours at 5500c and 320 PMa stress.

Keywords

• ti60/ti6246 dual titanium alloy
• isothermal deformation
• gradient heat treatment
• microstructure
• property