Effect of chemical ordering annealing on martensitic transformation and superelasticity in polycrystalline Ni-Mn-Ga microwires
Effect of chemical ordering annealing on martensitic transformation and superelasticity in polycrystalline Ni-Mn-Ga microwires
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DOI：
10.1016/j.jallcom.2015.05.118
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发表时间：
2015-10-05
影响因子：
6.2
通讯作者：
Peng, H. X.
中科院分区：
文献类型：
--
作者：
Qian, M. F.;Zhang, X. X.;Peng, H. X.
采用熔体萃取技术大规模制备了直径30-80μm的多晶Ni-Mn-Ga微丝。快速凝固的微丝表现出相当高的延展性和优异的形状记忆性能。在此，为了降低所提取的微丝中的缺陷密度、内应力和成分不均匀性，进行了逐步化学有序退火热处理，并研究了退火对马氏体相变、磁性能和超弹性行为的影响。结果表明，退火提高了相变温度并降低了相变滞后。这些与成分均质化、原子有序度的增加以及内应力和缺陷的减少有关。在机械测试过程中，退火处理后应力诱导马氏体 (SIM) 的形成发生在低得多的应力下。与提取的微丝相比，退火的微丝还表现出较低的超弹性滞后和较高的恢复率。退火后SIM应力的温度依赖性较弱，根据克劳修斯-克拉佩龙关系，这与焓变(Delta H)和相变温度变化有关。 (C) 2015 Elsevier B.V. 保留所有权利。
Polycrystalline Ni-Mn-Ga microwires of diameter 30-80 mu m were prepared by melt-extraction technique on a large scale. The rapidly solidified microwires exhibit a fairly high ductility and excellent shape memory property. Here, with the aim to reduce the defect density, internal stress and compositional inhomogeneity in the as-extracted microwires, a stepwise chemical ordering annealing heat treatment was carried out and the effect of annealing on martensitic transformation, magnetic properties and superelastic behavior were investigated. The results indicate that annealing increase the transformation temperature and decrease the transformation hysteresis. These are related to composition homogenization, increase of atomic ordering and decrease in internal stress and defects. During mechanical tests, the stress-induced martensite (SIM) formation took place at a much lower stress after annealing treatment. The annealed microwires also demonstrate a lower superelastic hysteresis and a higher recovery rate compared to the as-extracted microwires. The temperature dependence of SIM stress is weaker after annealing, which is related to the enthalpy change (Delta H) and phase transformation temperature change according to the Clausius-Clapeyron relation. (C) 2015 Elsevier B.V. All rights reserved.