Characterization of {001} antiphase boundary-type faults in an Al₆₇Ni₈Ti₂₅ intermetallic alloy

Abstract

Intermetallic alloys with compositions near Al₆₇Ni₈Ti₂₅ have the ordered cubic LI2 crystal structure. Features exhibiting stacking fault-like contrast have been observed on {001} planes in Al₆₇Ni₈Ti₂₅ after a homogenization anneal at 1323 K. A previous study revealed that the majority of these features are intrinsic stacking faults on {001} planes which result from dissociation of an a ₀ 〈100〉{001} dislocation. In the present paper the characteristics of a less-prevalent type of {001} fault in the same alloy (type II faults) are described. Analyses show that type II faults are {001} antiphase boundaries with an associated contraction of approximately 0·20a ₀ normal to the plane of the fault. The partial dislocations bounding the type II faults have Burgers vectors of (a ₀/2)〈110〉{001} and the total displacement vector of a type II fault is approximately (a ₀/10)〈552〉. Computer-simulated electron micrographs have been instrumental in identifying the fault characteristics. The apparent type II fault energy is 4 mJ m⁻².