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Large recoverable strain of more than several percent arising from superelasticity in shape memory alloys is important for actuators, sensors, and solid-state refrigeration. Here, we report a Ni50.0Mn31.4Sn9.6Fe9.0 magnetic microwire showing a giant tensile recoverable strain of about 20.0% along the ⟨001⟩ direction of austenite at 263 K. The recoverable strain represents the largest value reported heretofore in Ni-Mn-based shape memory alloys and is also larger than that of the Ni-Ti wire available for practical applications at present. This giant tensile superelasticity is associated with the stress-induced two-step transformation, and the transformation sequence could be L21 (austenite) → 6M (six-layered modulated martensite) → NM (non-modulated martensite), as suggested by the temperature-dependent in-situ synchrotron high-energy X-ray diffraction experiments and the transformation strain calculation based on the crystallographic theory of martensitic transformation. In addition, this Ni50.0Mn31.4Sn9.6Fe9.0 microwire shows a transformation entropy change ΔStr of 22.9 J kg−1 K−1 and has the advantages of easy fabrication and low cost, promising for miniature sensor, actuator, and solid-state refrigeration applications.

There is widespread attention to surface profile and modification of 304 stainless steel for research development and application. Here, a successful electrolytic plasma processing (EPP) technique has been developed for both surface pretreatment and coating deposition of 304 stainless steel. Representative images confirm that the number of the pits increases and the ravines gradually disappear on the steel pretreated by EPP with the increase of processing time and applied voltage. Moreover, there is an obvious enhancement in surface roughness of 304 stainless steel after EPP pretreatment. In the case of coating deposition, the further EPP modification conducted on the pretreated sample offers a simple and effective technique for the production of zinc coatings having the features of full coverage and homogeneous distribution. The results show that a zinc coating with a thickness of approximately 0.5 μm can be obtained on the 304 stainless steel by means of EPP for only 60 s.

High-performance magnetocaloric materials should have a large reversible magnetocaloric effect and good heat exchange capability. Here, we developed a Ni48.1Co2.9Mn35.0In14.0 metamagnetic shape memory microwire with a large and reversible inverse magnetocaloric effect. As compared to the bulk counterpart, the microwire shows a better combination of magnetostructural transformation parameters (magnetization difference across transformation ΔM, transformation entropy change ΔStr, thermal hysteresis ΔThys, and transformation interval ΔTint) and thus greatly reduced critical field required for complete and reversible magnetic-field-induced transformation. A strong and reversible metamagnetic transition occurred in the microwire, which facilitates the achievement of large reversible magnetoresponsive effects. Consequently, a large and reversible magnetic-field-induced entropy change ΔSm of 12.8 J kg−1 K−1 under 5 T was achieved in the microwire, which is the highest value reported heretofore in Ni-Mn-based magnetic shape memory wires. Furthermore, since microwires have a high surface/volume ratio, they exhibit very good heat exchange capability. The present Ni48.1Co2.9Mn35.0In14.0 microwire shows great potential for magnetic refrigeration. This study may stimulate further development of high-performance magnetocaloric wires for high-efficiency and environmentally friendly solid-state cooling.