High Temperature Deformation of a Fine-Grained and Particle-Dispersed V-2.3%Y-4%Ti-3%Mo Alloy

The high temperature deformation behavior of a fine-grained and particle-dispersed V-2.3%Y-4%Ti-3%Mo (mass%) alloy was investigated. The alloy was fabricated by powder metallurgical methods utilizing mechanical alloying and hot isostatic pressing (HIP), followed by annealing at 1273 K for 3.6 ks. Tensile tests were performed at temperatures from 873 to 1273 K at initial strain rates from 2.5 x 10(-5) to 1.0 x 10(-1) s(-1). X-ray diffraction analyses show that the HIPed and annealed specimens contain a significant amount of (Y, Ti)(2)O-3 and small amounts of YN, Ti2O3 and TiO. Transmission electron microscopy observations show that the matrix contains approximately 3%Ti and 3%Mo in solution and that the average diameters of the matrix grains and dispersoids are about 620 and 42 nm, respectively. Tensile test results show that the yield stress depends strongly on test temperature and strain rate. From the dependence of the yield stress measured at 1073 and 1273 K on plastic strain rate, it is found that the dependence is divided into three regions with different deformation controlling mechanisms: a recovery controlling process of a long range internal stress field associated with dispersed particle (the high-strain-rate region), grain boundary sliding (the medium-strain-rate region) and presumably solute atmosphere dragging (the low-strain-rate region). Effects of 4%Ti addition on the microstructures and high temperature deformation behavior are discussed.