The microstructure and properties of ultra-fine grained Ti-17 powder compact improved through isothermal forging

Abstract

The microstructure and properties of hot isostatic pressed (HIP-ed) Ti-17 powder compact were improved through isothermal forging with preferable deformation parameters provided by processing map. The processing map was established based on isothermal compression experiments which were conducted at temperatures from 810°C to 920°C and strain rates from 0.001s−1 to 1s−1. The established processing map ascertained the value of the efficiency of power dissipation, the flow stability region and the flow instability region at different deformation conditions. Based on processing map, the isothermal forging was conducted above and below beta transus temperature to fully densify the powder compact and simultaneously improve the microstructure. After isothermal forging in flow stability regions with preferable deformation parameters, the primary coarse grains of HIP-ed Ti-17 powder compact were thoroughly broken. Many ultra-fine dynamic recrystallized grains formed and uniformly distributed in beta matrix. Both experiment data and fracture morphology of tensile sample proved that the microstructure and properties of HIP-ed Ti-17 powder compact were largely improved during isothermal forging. Final properties of prepared ultra-fine grained Ti-17 powder compact even exceeded conventional casting and forging Ti-17 alloy.