Elastocaloric switching effect induced by reentrant martensitic transformation

Abstract

Vapor compression technologies widely used for refrigeration, heating, and air-conditioning have consumed a large fraction of global energy. Efforts have been made to improve the efficiency to save the energy, and to search for new refrigerants to take the place of the ones with high global warming potentials. The solid-state refrigeration using caloric materials are regarded as high-efficiency and environmentally friendly technologies. Among them, the elastocaloric refrigeration using shape memory alloys has been evaluated as the most promising one due to its low device cost and less of a demand for an ambient environment. General caloric materials heat up and cool down when external fields are applied and removed adiabatically (conventional caloric effect), while a few materials show opposite temperature changes (inverse caloric effect). Previously reported shape memory alloys have been found to show either a conventional or an inverse elastocaloric effect by the latent heat during uniaxial-stress-induced martensitic transformation. In this paper, we report a self-regulating functional material whose behavior exhibits an elastocaloric switching effect in Co-Cr-Al-Si Heusler-type shape memory alloys. For a fixed alloy composition, these alloys can change from conventional to inverse elastocaloric effects because of the change in ambient temperature. This unique behavior is caused by the sign reversal of latent heat from conventional to the re-entrant martensitic transformation. The realization of the elastocaloric switching effect can open new possibilities of system design for solid-state refrigeration and temperature sensors.

BCC-HCP-FCC Multiple Transformations and ε Loop in the Fe-Cr-Co-Mn System

“…This type of reentrant martensitic transformation has been observed in Co-based Heusler alloys. [66][67][68] Notably, e martensite is partially induced by water quenching and the martensitic transformation does not occur by further cooling using liquid nitrogen in this system, as confirmed in Fig. 4(e) and (f), although aging at 200-400 °C induces bainite.…”

Dissipation losses limiting first-order phase transition materials in cryogenic caloric cooling: A case study on all-d-metal Ni(-Co)-Mn-Ti Heusler alloys

“…However, the here reported and so far overlooked aspect of hysteresis for low-temperature magnetocalorics, leading to an irreversible and substantial absolute increase of Δ due to dissipation losses, significantly limits such an utilization, as Δ clearly dominates the thermal response at ≤ 50 K (see figure 5 (b)). In combination with similar irreversible, positive and directly measured Δ signals in inverse magnetocaloric Fe-Rh [34] at elevated temperatures, inverse elastocaloric Co-Cr-Al-Si [89] and conventional elastocaloric Ti-Ni-Cu-Al [90] as well as Ti-Ni-based, Cu-based and Ni-Mn-based shape memory alloys [91], we expect the effect to be neither material nor stimulus specific but fundamentally linked to phase transitions with hysteresis, underlining the universal importance of mastering hysteresis [92] in all caloric materials showing first-order phase transitions, especially at such low temperatures.…”

Caloric Effects Induced by Uniform and Non-uniform Stress in Shape-Memory Materials

“…This is a consequence of the fact that, in the superelastic region above the martensitic transition temperature, a larger threshold must be overcome to induce the transformation by application of a uniaxial stress than by bending. In real materials the difference of both caloric effects might be even larger due to the inverse response associated with the volumetric effect [12] that dominates the caloric response in the elastic deformation region of the parent phase.…”