Elevated temperature compressive slow strain rate properties of several directionally solidified NiAl-(Nb,Mo) alloys

Three NiAl-based alloys containing 3Nb-10Mo, 5Nb-10Mo or 13.6Nb-18Mo (at%) were directionally solidified to develop three dimensional Mo-based dendrit e networks. Examination of the alloys indicated that the desired chemistry was achieved for the 3Nb-10Mo and 5Nb-10Mo versions but the composition of the highly alloyed ingot was NiAl-14.6Nb-13.2Mo. The as-grown structure for all three materials consisted of three major phases: essentially unalloyed B2 crystal structure NiAl, Laves NiAlNb phase alloyed with similar to 8.5 Mo, and a bcc metallic Mo solid solution containing 27Nb-7Ni-7Al. Compressi ve properties were measured between 1200 to 1400K in air under constant vel ocity and constant load creep conditions with strain rates ranging from sim ilar to 10(-4) to similar to 10(-8) s(-1). The flow strengths of the two al loys with 10Mo were nearly identical and much weaker than those for NIAl-14 .6Nb-13.2Mo under all conditions. Comparison the properties of this latter alloy with other directionally solidified NiAl-based eutectics revealed tha t it was the strongest material under lower temperature/fast deformation co nditions, but this advantage was lost at higher temperatures and/or slower strain rates. (C) 1999 Elsevier Science Ltd. All rights reserved.