Microstructural Refinement and Mechanical Property Improvements of Ti-5AI-1Sn-1V-1Zr- 0.76Mo alloy by Equal Channel Angular Extrusion Processing

摘要

Severe plastic deformation (SPD) by equal channel angular extrusion (ECAE) was investigated as a way to produce ultra fine grain (UFG) microstructure in Ti-5Al-1 Sn-1V-1Zr-0.76Mo. DEFORM 3D Finite Element Model (FEM) was used to predict loads and strain distribution associated with ECAE which were validated experimentally The effects of resulting ultra fine grain microstructure on room temperature mechanical properties and high temperature super plasticity were investigated. ECAE processing: resulted in the conversion of coarse Widmanstatten structure to fine equiaxed microstructure with an average grain size of 4 μm. The alloy with fine grained equiaxed microstructure has 20- 25% higher yield strength, 15% higher ultimate tensile strength, and 50-100% higher % elongation to fracture and % reduction in area compared to the as received alloy containing coarse Widmanstatten microstructure. The ECAE processed alloy exhibits attractive superplastic formability charactersistics at 900-950℃ with m value > 0.4, flow stresses < 20 MPa, and superplastic elongations > 200%