Strain aging embrittlement of the ordered intermetallic compound NiAl

Abstract

The deformation behavior and fracture toughness of single crystals of the ordered intermetallic compound NiAl were investigated as functions of relatively low temperature thermal treatments. A strain aging embrittlement phenonenon, similar to that observed in mild steels, was identified. In the non-embrittled condition, tensile ductilities on the order of 7%–8% and fracture toughness values of 15–17 MPa m12 were obtained for crystals with a 〈110〉 axis tested at room temperature. Additional observations of serrated yielding during compression testing at temperatures between 100 and 200 °C are consistent with strain aging induced by the low temperature diffusion of interstitial impurities or constitutional vacancies to dislocations, thus rendering them immobile at room temperature.