Phase transformations in Ni ₃AI, Ti ₃AI and Ti ₂AINb intermetallics under shock-wave loading

Abstract
Phase transformations induced in Ni ₃AI, Ti ₃AI-based superalloy with an addition of niobium, and orthorhombic Ti ₂AINb aluminides by shock-wave loading were studied. The samples were subject to an impact of a steel plate. The maximum pressure on the surface of the samples was 100 GPa. The loading pulse was 1  s. It was shown that the Ll phase transformation took place in a single crystal of the superalloy containing 90% Ni ₃AI intermetallic phase. A banded structure passing through initial -cuboids and regions with twins, which were the DO ₂₂-phase, were detected. The B phase transformation was revealed in the polycrystalline Ti-25.6 at. % Al-10.3 at. % Nb alloy after shock loading. Long straight dislocations, which occasionally formed slip bands, were located in grains of the DO ₁₉ phase and fine particles of the B ₂ phase were present instead of interlayers. Fine particles of the B ₁₉ phase, which was disordered on niobium, were found in the polycrystalline orthorhombic Ti-25 at. % Al-22 at. % Nb alloy after loading. The particles were observed along boundaries of initial plates of the orthorhombic O-phase. These observations were compared with results obtained after quasistatic compressionshear loading and cold or hot rolling.