STRAIN-AGING EMBRITTLEMENT OF THE ORDERED INTERMETALLIC COMPOUND NIAL

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 embr ittlement phenonenon, similar to that observed in mild steels, was ide ntified. In the non-embrittled condition, tensile ductilities on the o rder of 7%-8% and fracture toughness values of 15-17 MPa m1/2 were obt ained for crystals with a [110] axis tested at room temperature. Addit ional observations of serrated yielding during compression testing at temperatures between 100 and 200-degrees-C are consistent with strain aging induced by the low temperature diffusion of interstitial impurit ies or constitutional vacancies to dislocations, thus rendering them i mmobile at room temperature.