BEHAVIOUR OF THERMO-MECHANICALLY TREATED CuZnAl-SMA

Original scientific paper Hot rolling of CuZn27Al4 shape memory alloy results in the forming of defects in austenitic crystals. The defects such as dislocation and deformed boundaries of austenitic grains affect both "classical" material properties and the specific properties related to shape memory. Rolled and quenched alloy (ausforming treatment) shows hardening proportional to the value of introduced deformation. By increasing the level of true plastic deformation not only the yield stress and tensile strength are increased but also the pseudo yield stress thus making the mechanically induced martensitic transformation more difficult. Besides, the ausforming treatment reduces all the transformation temperatures of the austenitic-martensitic reaction, thus expanding the temperature field of pseudo-elasticity. In spite of the hardening, the thermo-mechanically treated CuZn27Al4 alloy retains the pseudo-elastic shape memory so that favourable combination of strength and transformation behaviour can be achieved by the ausforming treatment, which is required in the majority of applications of these alloys.