Ultrahigh cyclability of a large elastocaloric effect in multiferroic phase-transforming materials

Abstract

Multiferroic phase-transforming alloys demonstrate intriguing multicaloric effects, but they are intrinsically brittle and their elastocaloric effect shows poor cyclability, which remains a major challenge for exploiting more efficient multicaloric refrigeration. Here, by employing a novel strategy of strengthening grain boundary, the cyclability of elastocaloric effect in the prototype Ni-Mn-based multiferroic phase-transforming alloys is strikingly enhanced by two orders of magnitude. Ultrahigh cyclability of a large elastocaloric effect is achieved. This not only paves the way for exploiting multicaloric effects for more efficient cooling, but also provides a strategy for overcoming the cyclability issues in the ubiquitous brittle intermetallic phase-transforming materials. IMPACT STATEMENTThe cyclability of elastocaloric effect in the prototype Ni-Mn-based multiferroic phase-transforming alloys has been strikingly enhanced by two orders of magnitude through employing the strategy of strengthening grain boundary. ARTICLE HISTORY

Recent Progress in Crystallographic Characterization, Magnetoresponsive and Elastocaloric Effects of Ni-Mn-In-Based Heusler Alloys—A Review

“…For instance, the eCE of 2 K remains stable with almost no degradation for more than 150 cycles in (Ni 51.5 Mn 33 In 15.5 ) 99.7 B 0.3 (Yang et al, 2017). Later, they realized an ultrahigh cyclability of eCE in the (Ni 51 Mn 33 In 14 Fe 2 ) 99.4 B 0.6 polycrystalline alloy, i.e., a ΔT ad of 5.6 K at 2700 loading-unloading cycles (Yang et al, 2019).…”

“…As discussed above, the NiMnIn-based alloys are intrinsically brittle due to the high covalency in chemical bonds, which greatly reduces the fatigue fracture resistance of the material and thus is detrimental to the cyclic stability of the eCE. Aimed at improving the mechanical properties of the NiMnIn-based alloys, several methods have been proposed to enhance the mechanical properties, such as grain refinement (Yang et al, 2017;Yang et al, 2019;Huang et al, 2020), grain boundary strengthening (Huang et al, 2015;Zhao et al, 2017b;Huang et al, 2019), introducing coarse columnar crystals with strong texture (Huang et al, 2015;Zhao et al, 2017a;Huang et al, 2019), and introducing a soft second-phase (Yang et al, 2015;Shen et al, 2018).…”

“…Thus, elevating the strength of grain boundaries could significantly improve the mechanical properties. Until now, the most effective method known for increasing the cohesion of grain boundary is microalloying with boron (Yang et al, 2017;Yang et al, 2019). Z. Yang et al reported that by microalloying with boron, as illustrated in Figure 15, the grain boundary cohesion can be increased; meanwhile, the grain size can be refined (Yang et al, 2017).…”

“…FIGURE 15 | Effects of the B microalloying on the microstructure of a NiMnIn alloy(Yang et al, 2019).…”

“…As can be seen from Table2, this ΔT ad belongs to the relatively high value of room-temperature eCE in the NiMnIn-based alloys. Z.Yang et al reported that by Fe doping, A f of 304 K of the Ni 51.5 Mn 33 In 15.5 alloy (e/a = 7.93) is shifted to 319 K in the Ni 51 Mn 33 In 14 Fe 2 alloy (e/a = 7.99)(Yang et al, 2019). Under this substitution, ΔT ad was increased from 3 K of Ni 51.5 Mn 33 In 15.5 to 5.7 K of Ni 51 Mn 33 In 14 Fe 2 under 350 MPa.…”