The High Intrinsic Creep Strength of Non-Stoichiometric Ni2Alti

Abstract

It has been demonstrated (1) that the creep strength of the B2-type structure alloy NiAl (β-phase) can be enhanced to a remarkable degree by the addition of Ti which promotes the formation of the Heusler-type structure phase Ni2AlTi(β’). This phenomenon was attributed to the stabilization of dislocation networks at the semi-coherent (∼1%mismatch) phase interfaces. Now, recent observations are presented suggesting that this strengthening actually arises from the high intrinsic creep strength of the non-stoichiometric β and β’ phases.Fig. 1 shows creep strength at 1000°C as a function of Ti content for a series of alloys along the NiAl-Ni2AlTi tie-line; creep strength is defined as the stress to maintain a steady state rate of 10-7 sec-1. The phase regions along the tie-line were determined from precise lattice parameter measurements.