Microstructure coarsening behavior of Ti-17 alloy with equiaxed alpha during heat treatment

Static coarsening behavior of Ti-17 alloy with equiaxed alpha microstructure was investigated. For this purpose, Ti-17 billet with a fully lamellar alpha microstructure was firstly forged in the two-phase field to break down the lamellar alpha structure. Then alpha/beta heat treatments were conducted at temperatures of 820 degrees C and 860 degrees C for times range from 10 min to 8 h followed by water quenching. Microstructure observations showed that alpha particle size increased with time during heat treatment, and it was more apparent at the higher temperature. Microstructure coarsening behavior during static heat treatment was analyzed by quantitative metallography. Quantitative analysis indicated that the rate of static coarsening decreases with heat treatment time. The coarsening of Ti-17 alloy with equiaxed alpha during heat treatment followed (r) over bar (3)(alpha) - (r) over bar (3)(alpha 0) vs t - t(0) kinetics, which is a classical bulk diffusion (volume-diffusion-controlled) behavior. Static coarsening behavior of Ti-17 alloy in this paper could be interpreted in terms of the modified Lifshitz-Slyosov-Wagner (LSW) theory. Furthermore, the coarsening rate constant during static heat treatment could be reasonably predicted by the modified Lifshitz-Slyosov-Wagner (LSW) theory. (C) 2014 Elsevier B.V. All rights reserved.