Processing and properties of mechanically alloyed Ni(Fe)Al-Al₂O₃-AlN

Abstract

Ni(Fe)Al powders containing a homogeneous distribution of in-situ formed A1N and A1₂O₃ dispersoids were produced by a mechanical alloying process in a controlled atmosphere using a high energy attrition mill. The powders were successfully consolidated by either the hot pressing or hot extrusion process. The phase information investigated by TEM, XRD and a modified TGA analysis reveals that Fe can be soluble up to 19.2% to the NiAl phase(β) at room temperature after the MA process. Subsequent thermomechanical treatment under specific conditions was tried so as to induce a secondary recrystallization to improve the high temperature properties. However, no clear evidence of abrupt grain coarsening was obtained, presumably due to the restricted condition for the boundary break-away mechanism in this material. The mechanical properties in terms of strength at room temperature as well as at high temperatures were shown to have improved through the addition of AlN, and room temperature ductility was also shown to have improved by the precipitation of the second phase of α in this material.