Elasto-Caloric Fatigue: Size Effects – EFASIE2

The need for efficient, environmentally-friendly heating and cooling systems is becoming a priority worldwide, saving global energy for housing appliances. The use of heat pumps based on solid-state phase transformation (elasto-caloric effect) is promising for this purpose. Among all materials, copper-based alloys are the best candidates in terms of material resources and CO2/kg emissions. However, fatigue ageing needs to be increased (106 cycles required, instead of around 104 reported) before realistic devices can be developed. We propose to develop new compositions verifying 'crystallographic supercompatibility' criteria and to validate them from the microscopic to the macroscopic scale. A multi-scale approach varying the composition and the sample size as well as internal interface length is proposed and tested using nano- / micro- / macro-mechanical tests. For a better understanding of the fundamental mechanisms, characterization of crystallographic structures and the deformation field in the structures will be carried out, in particular using novel and advanced synchrotron radiation techniques. Optimizing elastocaloric functional properties of Cu-alloys with exceptional fatigue resistance is the objective of this experimental project since materials is clearly the bottleneck for using already designed heating/cooling devices.