Influence of grain size on the creep behavior of HfC-dispersed NiAl

Rapid solidification technology has been utilized to produce a NiAl-4(wt.%)HfC composite containing about 0.3 vol.% HfC as dispersed 50 nm particles. Study of the 1300 K compressive creep properties demonstrated that the initial, small grain size microstructure was unstable under slow strain rate deformation conditions. The grain growth which occurred during testing led to considerable strengthening. Subsequent measurements of the creep properties of the coarse grained specimens revealed that this strength was achieved by a large increase in the activation energy for deformation without any change in the stress exponent. Based on this work it is concluded that large grain microstructures will be required for optimum elevated temperature creep properties in dispersed NiAl.