J. Phys. IV France 07 (1997) C5-311-C5-316
Improvement of Hardness and Microstructures by Ageing in Shape Memory CuAlNi AlloysA. Aydogdu, Y. Aydogdu and O. Adigüzel
Department of Physics, Firat University, 23169 Elazig, Turkey
The shape memory CuAlNi alloys, having a composition near that of Cu3Al, exhibit disorder-order transition from the disordered bcc β-phase to the ordered β1-phase (DO3 type) at high temperatures. Although the β1-phase is a non-equilibrium phase, it nonetheless remains stable at room temperature upon quenching from the high temperature β-phase. At the lower temperatures, the β1-phase itself undergoes martensitic transformation and displays layered structure called M18R. The influence of ageing on two CuAlNi β-phase alloys was studied by measuring the time dependence of hardness, lattice parameters and by optical microscopy observation at room temperature. Hardness shows a trend to decrease with the ageing duration due to the formation of precipitation, and grain size is also affected by ageing.
© EDP Sciences 1997