Analysis of the Elevated Temperature Plastic Flow Response of Ti-6Al-4V Produced via the Hydrogen Sintering and Phase Transformation (HSPT) Process

Abstract

An analysis pertaining to hot deformation behavior was conducted on two unique titanium alloy microstructures. Each product was manufactured from commercially available blended elemental Ti-6Al-4V powder, consolidated by sintering in vacuum or hydrogen. The initial microstructures produced by these distinctive sintering atmospheres are represented by a coarse lamellar structure (produced by vacuum sintering) and a very fine lamellar structure [produced by Hydrogen Sintering Phase Transformation (HSPT)]. Performance of these materials was assessed by simulating representative titanium breakdown and conversion during thermomechanical processing through elevated temperature compression testing on a Gleeble® 3500 Hydrawedge II® system. Compression tests were performed on cylindrical specimens at sub and near-transus temperatures (850 °C, 900 °C, 950 °C, and 1000 °C) and at moderate strain rates of 0.01 and 0.10 s−1. The very fine lamellar microstructure exhibited similar flow behavior compared to the coarse lamellar structure, although with a typically slightly higher peak stress and greater degree of flow softening. In addition, the microstructure produced by HSPT retained a fine, equiaxed structure upon deformation, making it highly suitable for powder-based thermomechanically processed titanium alloy products.