Enhanced elastocaloric performance and cyclic stability of elastocaloric effect in Mn and Y co-doped all-d-metal Co-V-Ti Heusler alloy

Abstract

The all- d -metal Co-V-Ti Heusler alloy, due to its excellent mechanical and elastocaloric properties, shows great application potential in the field of elastocaloric refrigeration. However, the cyclic stability of elastocaloric effect (eCE) of such alloys still needs to be further improved, and developing elastocaloric refrigeration materials that possess both a large adiabatic temperature change (Δ T ad ) and excellent cyclic stability of eCE still holds significant advantages. Based on the all- d -metal Co-V-Ti Heusler alloy, this study achieved an innovative breakthrough in material performance by simultaneously adding Mn and Y elements. The results show that through composition optimization, the cast (Co 45.5 V 37.5 Ti 16.7 Mn 0.3 ) 99.9 Y 0.1 alloy exhibits the most superior performance, with a Δ T ad of up to −10 K under a stress of 600 MPa, significantly outperforming the reference Co-V-Ti alloy. This is attributed to the strong preferential orientation, which increases the volume fraction of stress-induced martensitic transformation. In addition, due to the combined effects of precipitation strengthening and fine-grain strengthening, the fracture strength and toughness of this alloy reach 1819 MPa and 35.77 %, respectively. Notably, after 4050 mechanical cycles under a stress of 700 MPa, the alloy exhibited minimal reduction in Δ T ad , decreasing from −10.55 K to −9.36 K, demonstrating that this alloy has excellent cyclic stability of eCE. The number of elastocaloric cycles of this alloy far exceeding that of the reference alloy, and the Δ T ad has increased significantly. The enhanced cyclic stability of eCE is mainly caused by the low dislocation density accumulation. Moreover, the synergistic effect of the B2 matrix and the V-rich secondary phase, as well as dislocation strengthening, also ensures the alloy's cyclic stability of eCE. The results show that the strategy of Y micro-alloying combined with Mn doping enables the development refrigeration materials with both a large Δ T ad and excellent cyclic stability of eCE.