Deformation twinning was studied, in the '-phase of the single-phase Ni3Al-B and the 2-phase Ni-Fe-Al alloy, by means of transmission electron microscopy. The former was shock-loaded to a stress of 14GPa, and the latter was dynamically deformed at a strain rate of 3000/s to a total accumulated strain of 16%. In both materials, twins were found to form only in grains with the L12 superlattice structure and extended completely across the grains. In the 2-phase alloy, no twins occurred in grains with the B2 superlattice structure. An analysis of the twins showed that the K1 twinning plane was {111}, with a 1 twinning direction of <112>. This was usually found in disordered face-centered cubic metals. It was proposed that the 2 direction in the second undistorted plane, K2, was <110>, which avoided the need for atomic shuffling. The twinning mechanism which was necessary for this twin plane, and the alternative 2 direction of <112> which required shuffles, was considered. Extensive planar slip on {111}-type planes was also seen in both materials, and in both the B2 and the L12 grains of the 2-phase alloy. A high density of stacking faults was observed in the shock-loaded single-phase alloy.

A Description of Deformation Twinning in Dynamically Deformed and Shock-Loaded Polycrystalline Ni3Al. Albert, D.E., Gray, G.T.: Philosophical Magazine A, 1994, 70[1], 145-58