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.
The 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.
The magnetocaloric effect and the elastocaloric effect in a polycrystalline all‐d‐metal Ni37Co9Fe4Mn35Ti15 magnetic shape memory alloy are investigated. The alloy undergoes a transition from ...ferromagnetic austenite to weak‐magnetic martensite near room temperature. It exhibits a maximum magnetic entropy change of 8.4 J Kg−1 K−1 under the magnetic field of 3 T. Moreover, a maximum temperature change of 6.3 K associated martensite transition is obtained at room temperature by loading the uniaxial stress of 400 MPa. These results suggest that the alloy is the promising candidate for new solid‐state refrigeration materials.
The Ni37Co9Fe4Mn35Ti15 undergoes a transition from ferromagnetic austenite to weak‐magnetic martensite with the application of the magnetic field and uniaxial stress. It is found that the alloy exhibits a magnetic entropy change of 8.4 J Kg−1 K−1 under the magnetic field of 3 T and a maximum temperature change of 6.3 K under 400 Mpa during the transition.
Herein, the magnetic properties and elastocaloric effects of Cu 70 Al 19 + 0.5 x Mn 11−0.5 x ( x = 0, 1, 2, 3) alloys are investigated. The resistance versus temperature curves indicate that the ...phase transition temperature increases as the Mn content decreases. In particular, the Cu 70 Al 20.5 Mn 9.5 alloy exhibits a phase transition temperature close to room temperature. Therefore, the elastocaloric effects of this alloy are examined under stresses ranging from 200 to 500 MPa. The results show that the adiabatic temperature change of the alloy under a stress of 500 MPa reaches 9.8 K. Furthermore, the magnetization curves at 300 K reveal that the magnetic properties of the alloy significantly improve after undergoing low‐temperature aging treatment. The X‐ray diffraction patterns show that this improvement can be attributed to the transformation of the β 1 phase to the ferromagnetic phase β 3 . Overall, the Cu 70 Al 20.5 Mn 9.5 alloy demonstrates elastocaloric and magnetic properties comparable to those observed in certain Ni–Mn‐based alloys.
With the rapid development of solid-state refrigeration technology, elastocaloric materials face higher requirements, such as a higher elastocaloric effect (eCE), better mechanical properties, and ...simpler and faster large-scale preparation. In this work, we propose a composition design strategy for Mn-doped Co–V-Ga shape memory alloys, which can enhance both the eCE and the mechanical properties. We combine first-principles calculations and experiments to demonstrate this strategy. Our results reveal that the lattice distortion caused by the difference in atomic radii produces a solid-solution-strengthening effect within the alloy, impeding dislocation motion and significantly improving the mechanical properties. Through composition optimization, the low-cost Co51.7V31.3Ga14.75Mn2.25 as-cast polycrystalline alloy exhibits a large adiabatic temperature change (ΔTad) of −11.2 K at room temperature, while its maximum compressive strength and strain can reach up to 1859 MPa and 26% at room temperature, respectively. Importantly, the alloy exhibits excellent cycle stability, and its ΔTad does not decay after 100 loading and unloading cycles, indicating that it has the potential for practical application. Further comparison with the annealed sample shows that the secondary defects deteriorate the ΔTad of the alloy. Our research provides an effective strategy for the simple, rapid and large-scale production of as-cast eCE alloys.
This article discusses experimental data and their theoretical interpretation concerning the volume magnetostriction, spontaneous magnetostriction, variation of magnetization under the action of ...pressure, and elastocaloric effects in rare-earth metals, as well as their alloys and compounds. Particular attention is paid to the region of phase transitions. The volume magnetostriction ω of true magnetization was investigated near the Curie temperature Θ as a function of magnetization and determined from the change of magnetostriction under the action of pressure. From these data we obtained the dependence of the exchange integrals on the unit cell volume. Giant volume magnetostriction and magnetoelastic elastocaloric effects were discovered in the rare-earth metals and alloys in the region of their magnetic phase transitions. It was established that giant volume magnetostriction in RCo
2
compounds is caused by a critical increase of the magnetic moment of the 3d sublattice of cobalt in magnetic fields that exceeds the critical field at
T
> Θ. Giant volume magnetostriction in R
2
Fe
17
compounds near the temperature Θ is shown to occur due to strong deformational dependences of exchange interaction and the value of the 3
d
electron bandwidth.
PDF
