Temperature and microstructural dependence of the deformation of a high Nb Ti-Al alloy

Compression testing of a Ti-44-Al-11Nb alloy was carried out at various temperatures and for different microstructures. Annealing was done at temperatures from 1,000 C to 1,500 C to produce the unrecrystallized, duplex (gamma grains plus lamellar colonies) and the fully lamellar microstructures. Sample of each of these microstructures were then tested in air at room temperature and at various temperatures from 1,000 C to 1,300 C. Results indicate that successively higher temperature anneals produce increasing grain or colony sizes from 138 μm in the unrecrystallized microstructure to 1,017 μm in the fully lamellar microstructure. A sequentially lower yield stress was produced on samples tested at increasingly higher temperatures for a given microstructure. In addition, a minimum yield stress on each yield stress vs temperature curve was recorded for the duplex microstructure with a colony size of 154 μm. One promising result was a sample of this microstructure tested at room temperature, where a yield stress of better than 800 MPa and a compressive strain at the cessation of testing of better than 14 pct were obtained