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The room temperature ductility of an L12-type A13Ti alloy containing 7.5 at.% Fe has been improved substantially by hot isostatic pressing (HIP) after arc casting. This L12-type alloy can be deformed in compression to 11.4 % at room temperature after HIPing, retaining the original shape of compressive specimens, while compressive specimens without HIPing following heat-treatment for homogenization (HHT) fracture into small pieces when deformed to similar strain. At temperatures higher than 400°C, specimens for both HHTed and HIPed conditions show similar behavior, having strains to failure of greater than 12 % plastic strain. Fracture occurs at room temperature by brittle transgranular cleavage with a smooth surface in HHTed specimens, while in HIPed specimens, fracture occurs by both transgranular and intergranular modes. Transgranularly fractured surfaces in the latter case have rough surfaces with fine structure, indicating ductile fracture as compared with that for HHTed specimens. In both HIPed and HHTed specimens, no fracture surfaces are flat and parallel to any crystallographic planes. High resolution electron microscopy has revealed that a pair of superlattice partial dislocations on a (111) plane have a spacing of approximately 11 nm (2–3 times larger than that for Al-23Ti-6Fe-5V) giving an antiphase boundary energy of 95 mJ/m2. Since this energy is relatively low, the present alloy may be ductile because of its ready emission of dislocations at crack tips, according to the Rice-Thomson criterion. Improvement of room-temperature ductility of this alloy is attributed primarily to the reduction of a large population of cavities formed upon arc casting.

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Cyclic flow‐stress measurements at room temperature are performed on Ni3Ge single crystals as a function of stress and strain amplitude. The cyclic flow‐stress is found to be higher in compression than in tension for stress orientations [345] and [245]. This flow‐stress asymmetry became greater with increasing plastic‐strain amplitude when {111} slips are operative. However, in a higher strain regime (>1 × 10−4) where {001} slip systems are also activated, the stress asymmetry for orientation [345] became smaller with increasing plastic‐strain amplitude. For orientation [2 3 16], the cyclic flow‐stress is higher in tension than in compression. The cyclic‐stress asymmetry properties can be attributed to the thermally activated cross‐slip of screw dislocations from {111} to {010}. The decrease in the stress asymmetry observed in orientation [345] at the higher strain regime (>1 × 10−4) is probably caused by the change in the dominant slip systems from the octahedral to cube slips.