Microstructure investigation and mechanical properties of Ti-6Al-2Sn-4Zr-6Mo alloy processed by hot rolling and solution treatment

Abstract

The Ti-6Al-2Sn-4Zr-6Mo (Ti-6246) titanium alloy is categorized as one of α + β titanium alloys group, which plays an important role in the aerospace applications. This study aims to find out the optimal thermomechanical processing route to obtain a good balance of strength, ductility and fracture toughness. The Ti-6246 alloy was hot-deformed at a temperature of 900°C, with a total deformation degree of approximately 60%, and heattreated by a solution treating at temperatures between 800°C -1000°C for 18 minutes. The microstructural evolution, mechanical properties and fractography analysis were investigated. Results revealed that the volume fraction of the primary α (αp) phase decreases progressively until it is completely dissolved with increasing solution temperature; the secondary α (αs) phase increases whereas its width decrease with increasing solution temperature, and also the yield stress and ultimate tensile strength decrease with increasing solution temperature. A good balance of ultimate tensile strength and ductility was obtained in the case of a solution temperature of 900°C, which showed a tensile strength close to 812±4 MPa and an elongation close to 11.1±2.4 %. The fine αs phase facilitates the paths of crack propagation, meaning decrease the crack propagation resistance and decrease the ductility and fracture toughness.