The temperature dependence of elastocaloric cooling properties of a NiTi alloy with a grain size gradient, which was obtained by cold rolling and subsequent laser surface annealing, was evaluated and compared with those of coarse-grained and as-rolled NiTi. Results show that the adiabatic temperature change () and cooling efficiency of the gradient-structured NiTi are significantly enhanced over a wider temperature span (), making it a superior elastocaloric refrigerant candidate. Detailed analyses show that while the fine grains present in the core of NiTi sheets reduce the global martensitic autocatalytic nucleation potency and increase strength to broaden , the coarser grains near the surfaces accommodate interlayer deformation to improve . The work provides a method for overcoming the trade-off between cooling capacity and service temperature span of elastocaloric materials.

中文翻译：

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微观结构梯度 NiTi 合金中弹热效应的温度依赖性

通过冷轧和随后的激光表面退火获得的具有晶粒尺寸梯度的 NiTi 合金的弹热冷却性能的温度依赖性进行了评估，并与粗晶和轧态 NiTi 合金进行了比较。结果表明，梯度结构 NiTi 的绝热温度变化 () 和冷却效率在更宽的温度范围 () 内显着增强，使其成为优异的弹热制冷剂候选者。详细分析表明，虽然NiTi片芯部存在的细晶粒降低了整体马氏体自催化成核能力并增加了强度以使其变宽，但靠近表面的较粗晶粒可适应层间变形以提高强度。这项工作提供了一种克服弹性热材料的冷却能力和使用温度范围之间的权衡的方法。