Investigations of fatigue mechanisms in elasto-caloric CuZnAl

The need for efficient and environmentally friendly heating/cooling systems is increasing. The use of heat-pump based on solid state phase transformation are promising, in particularly elasto-caloric materials [1]. CuZnAl alloys are on a material resource and CO2/kg emission perspectives among the best candidates [2]. Elasto-caloric effect is based on a non displacive crystallographic transition between a high symmetry crystal structure, austenite (high temperature cubic phase) and lower symmetry one, martensite (monoclinic), activated around room temperature thermally or by shear stress, (figure a). The main bottleneck toward applications is the short fatigue life, due to the lattice mismatch between both phases. Optimizing the composition to achieve high lattice compatibility would allow extending the life to 10⁷ cycles. Using Dark Field Xray Microscopy we propose to measure the accumulated local microstrain and defects generated in austenite after a large number of thermal cycles.