Consolidation of a rapidly solidified titanium alloy by hot isostatic pressing

Abstract

Materials produced by two rapid solidification techniques, the plasma rotating-electrode process (PREP) of Nuclear Metals Inc. and the melt extraction process of General Electric Corporate Research and Development, have been consolidated by hot isostatic pressing (HIP). Microstructures show that, for quench rates of approximately 10 2°Cs −1 associated with PREP, there is pronounced segregation of phases whereas, for the higher quench rate (10 5°Cs −1 of melt-extracted microstructures, this massive segregation is absent. It is to be expected that in the powder metallurgy PREP material the finer particles would experience the higher quench rates and hence would show less phase separation than coarser particles; material consolidated in this study from the finer-particle PREP fraction did exhibit a finer grain structure and the best combination of strength and ductility. This investigation also showed that the hydrostatic stress provided by HIP lacked the shear component needed to provide the strain required to ameliorate the deleterious effects of chemical and structural inhomogeneities and prior particle or filament boundaries present in the powders and ribbons used.