The effect of microstructural defects induced by mechanical milling has been studied in a Ni–Mn–In–Co metamagnetic shape memory alloy. The martensitic transformation and Curie temperatures do not change with grinding, thus pointing out to a null variation of long range atomic order as a consequence of the deformation. Nevertheless, the enthalpy change of the martensitic transformation highly decreases. This, and the large thermal stabilization of the martensite (with shifts on the temperature of the first reverse martensitic transformation up to 60 K), indicate the presence of a huge amount of internal stresses and microstructural defects in the obtained micro-particles. The presence of such defects considerably affects the saturation magnetization in austenite whereas almost no effect is observed in martensite. The magnetocaloric effect has been evaluated in samples with three different particle sizes. In spite of the MCE value is lower than in the bulk, the broader temperature range for the martensitic transformation in the powders makes the relative cooling power be comparable to that in the bulk. The as-milled micro-particles can be then considered as good preliminary candidates for magnetic refrigeration applications at the microscale.

在Ni–Mn–In–Co超磁性形状记忆合金中研究了机械铣削引起的微结构缺陷的影响。马氏体相变和居里温度不会随研磨而变化，因此指出由于变形，长程原子序的零变化。然而，马氏体相变的焓变大大降低。这以及马氏体的大热稳定性（随着第一次逆马氏体相变的温度变化直至60 K），表明所获得的微粒中存在大量的内部应力和微观结构缺陷。这种缺陷的存在会严重影响奥氏体中的饱和磁化强度，而在马氏体中几乎没有观察到影响。磁热效应已在三种不同粒径的样品中进行了评估。尽管MCE值低于本体，但粉末中马氏体相变的温度范围较宽，使得相对冷却能力与本体中的相对冷却功率相当。然后，可以将研磨后的微粒视为用于微尺度磁制冷应用的良好的初步候选物。