Influence of Preloading and Deformation on the Grain Structure and Strength of the Ni3Al Intermetallic Compound Synthesized under Pressure

Resumo

We have studied the influence of a preload applied to a starting elemental powder mixture and the strain in the product of high-temperature synthesis during a bulk exothermic reaction on the grain structure of the Ni₃Al intermetallic compound and the temperature dependence of its strength. The results demonstrate that, during the bulk exothermic reaction responsible for the formation of the intermetallic compound under pressure in a closed press die, the average grain size varies along a vertical cut, from the minimum value on the upper and lower surfaces of the synthesized sample to the maximum value in its central part. As the preload applied to the starting powder mixture is raised, the average grain size decreases, whereas the general character of the grain size distribution in a cross section of the sample remains unchanged. Deformation of the high-temperature synthesis product in a press die with partial extrusion causes an appreciable grain size reduction, significantly averaging the grain size in the bulk of the synthesized sample, and raises the tensile strength of the intermetallic compound in the temperature range 20–1000°C.