Preparation, Microstructure and Properties of Ti-6Al-4V Rods by Powder Compact Extrusion of TiH_2/AI_(60)V_(40) Powder Mixture

摘要

Ti-6Al-4V (wt.%) alloy rods were prepared successfully using a low-cost and short powder metallurgy process that involves mixing TiH_2 and Al_(60)V_(40) powders, compacting the powder blend and extruding the powder compact at elevated temperatures. The microstructure and mechanical properties of Ti-6Al-4V alloy and the effects of particle size, oxygen content and heat treatment on them were investigated. The results showed that the microstructure and homogeneity of the extruded rods were strongly affected by the particle size of TiH_2/AI_(60)V_(40) powder blends. By changing tumbler mixing into low-energy ball milling, the TiH_2/Al_(60)V_(40) particle size decreased, and the volume fraction of undissolved V rich particles in the microstructure of the extruded rod substantially decreased from 8.6% to zero. High yield strength and ultimate tensile strength of 1154 and 1353 MPa respectively with a moderate elongation to fracture of 3.6% are achieved with the Ti-6Al-4V rod prepared by using the powder blend. The extruded Ti-6Al-4V rod prepared using the ball milled powder had a very high strength, but limited ductility due to a high oxygen content. Solution treatment and aging slightly increase the strength of Ti-6Al-4V rods at the cost of dramatic decrease of ductility.