Mechanical properties of spark plasma sintered Nb-Al compacts strengthened by dispersion of Nb2N phase and additions of Mo and W

Mechanically alloyed and blended Nb-Al-N powders were sintered by the spark plasma sintering process, and their microstructure and mechanical properties were investigated. All of the Nb-Al-N compacts consisted of phases in the Nb-Al system in which the Nb2N phase was dispersed. The microstructure of blended powder compacts was much coarser than that of mechanically alloyed powder compacts. The compacts obtained by sintering powder produced by crushing blended powder compacts have finer microstructure, higher hardness, and higher fracture toughness than blended powder compacts. The strength of Nb-Al-N compacts increases with increasing the fraction of AlN added to the Nb powder, while their fracture toughness at room temperature decreases. As for the Nb-Al-Mo and Nb-Al-W system, the effect of solid-solution hardening of W was larger than that of Mo, and Nb-15Al-40Mo compact has the highest strength at room temperature and 1273 K among Nb-15Al-xMo compacts. (C) 1999 Elseiver Science Ltd. All rights reserved.