ORIENTATION DEPENDENCE OF SIGMA-T PHASE-DIAGRAMS FOR MARTENSITE TRANSFORMATIONS IN CU-AL-NI SINGLE-CRYSTALS

The orientation dependence of the martensitic transformations beta(1) < - > gamma'(1), beta(1) < - > beta'(1) and beta'(1) < - > gamma'(1) induced under stress have been studied in Cu-14.2Al-4.1Ni single crystals using thermal cycling and tensile deformation. The non-equilibrium and equilibrium sigma-T phase diagrams for middle, [100], [110] and [111] oriented crystals are presented and discussed, the orientation dependence of the phase transformations being analysed on the basis of the Clausius-Clapeyron equation. The results indicate that the geometrically most convenient Variants of martensite farm during the beta(1) < - > beta'(1) transformation. For the beta(1) < - > gamma'(1) transition, some less favourable martensite variants seem to be preferred.