Slip creep of Ni 3Ga

Abstract

The creep strength of L1{sub 2} alloys is a fundamental property to optimize if this class of materials is to fulfill any future role in high-temperature structural applications. Workers experimenting on compression creep specimens of single crystal and polycrystalline, Ni{sub 3}Al have reported an inverse creep response. Inverse creep is rather like tertiary creep in that the creep rate increases rapidly with strain, except that it occurs in compression at small strains involving no structural degradation. This type of creep response is of significance to future applications of L1{sub 2} alloys. Specimens exhibit a primary region of decelerating creep which reaches a short period of steady-state minimum creep rate followed by inverse creep. The aim of this research is to investigate the creep property of Ni{sub 3}Ga in a temperature range covering the yield stress peak, with particular reference to inverse creep and its models. The experimental method will involve the use of prestraining at constant strain-rate to inject a different density of KW locked screw dislocations into single crystals of Ni{sub 3}Ga followed by creep testing under a constant compressive load. The subsequent creep rate, and that of virgin Ni{sub 3}Ga specimens, will be discussed with reference to slipmore » line analyses and Transmission Electron Microscopy (TEM) investigations and related to the current models.« less