Effect of the method of introduction of Y2O3 into NiAl-based powder alloys on their structure: II. Mechanical activation

Abstract

Effect of mechanical activation of NiAl powders produced by calcium hydride reduction in an attritor and a ball mill on the specific surface, the oxygen concentration, the strain hardening, and the coherent domain size (CDS) of the powders is studied. It is found that the powder specific surface milled in the attritor for 10–15 h is larger by a factor of 1.7–1.8 and the oxygen concentration in a powder is lower by a factor of 1.35 as compared to the its milling in the ball mill for 150 h. The powders milled in the attritor for 15 h have the level of microstresses higher by a factor of ∼2.4 and the CDS smaller by a factor of 2 as compared to the powder treated in the ball mill for 150 h. When milling a powder in the attritor, the milling time decreases by a factor of 10 and the degree of powder refinement increases, which improves the technological characteristics of the powders. As a result of the combination (in one operation) of mechanical activation of an NiAl intermetallic matrix powder in the attritor and the introduction of dispersed particles of a refractory oxide Y2O3 powder, the produced composite alloy has a density close to the theoretical one and has no aggregates of dispersed oxide particles at grain boundary junctions. Submicro- and nanosized oxide particles are homogenously distributed in the intermetallic matrix volume, which is characterized by a homogeneous distribution of nickel and aluminum.