Microstructures and Mechanical Properties of (NiAl+Ni_3Al) Two-Phase Intermetallic Compounds Produced by MA-HIP Process

摘要

The (Ni_3Al+NiAl) intermetallic compounds were produced by MA-HIP method. There are two cases for the sintered specimens; the one was produced using only elemental powders (EP specimen) and the other was produced using both NiAl prealloyed and nickel powders (PP specimen). Those alloys were subjected to the heat refining process. The microstructural change and mechanical properties were investigated. It was found that the fine particles with the size of less than 3#mu#m were obtained by MA process. EP specimen showed very fine microstructures with almost full density. On the other hand, PP specimens showed higher relative density with increasing HIP temperature. After heat-refining treatment, EP specimen had fine structure, since the size of the prior #beta# grains and the width of lamella decreased comparing with PP specimens. There was the tendency for the mechanical properties of PP specimens to approach those of EP specimen with increasing HIP temperature. The strain rate sensitivity exponent, m value, was found to be about 0.52 for EP specimen and 0.34 for PP specimen at 1073K. This high m value suggests the occurrence of superplastic deformation especially in EP specimen.