Microstructure Control of a TiAl Base Alloy Prepared by Reactive-Sintering by Low Temperature HIP

Abstract

The changes in structure and properties of a hot-extruded mixture of Ti and Al-Mn alloy elemental powders during the reactive sintering were examined. The aim of this investigation was to change the maximum heating temperature of HIP treatment from the conventional 1653 K to lower temperatures.
It was found that the density of 973 or 833 K HIP’ed material increased by subsequent heat treatment under atmospheric pressure. Especially, when the 973 K HIP’ed material was heat-treated at 1653 K, the density became comparable with that of 1653 K HIP’ed one. An interesting property was found in the 973 K HIP’ed material, i.e. it can easily deform under a low applied stress at 1273 K. This enables the microstructure of the 973 K HIP’ed material to be controlled widely by using thermomechanical treatment. Fully lamellar structure of 973 K HIP’ed material obtained by heating at 1653 K exhibits a texture. The texture is weakened by the 1273 K forging before heating.