1000-1300 K SLOW STRAIN RATE PROPERTIES OF NIAL CONTAINING DISPERSED TIB2 AND HFB2

Abstract Rapid solidification technology was used to produce NiAl containing dispersions of fine TiB 2 or HfB 2 particles in an effort to improve the elevated temperature strength of this intermetallic. As-melt spun ribbons of NiAl2TiB 2 were pulverized, and the resulting powders were densified by extrusion at 1420 K with a 16:1 reduction ratio, while NiAl2HfB 2 was initiall;y consolidated by hot isostatic pressing at 1505 K and 207 MPa for 4 h followed by forging 65% at 1535 K. Both materials were compression tested in air between 1000 and 1300 K under constant velocity conditions at nominal strain rates ranging from 2 × 10 −3 to 2 × 10 −7 s −1 . NiAl2HfB 2 displayed steady state behavior under all test conditions while NiAl2TiB 2 exhibited diffuse yielding at 1000 K and generally slow, continuous work hardening at the higher temperatures. Analysis of the flow stress-strain rate data indicated that both materials behaved normally, and deformation could be described by temperature compensated power laws. HfB 2 was found to be a more effective strengthening addition than TiB 2 .