An interpretation of the kinetics of martensitic transformation in a Ni45Co5Mn36.5In13.5 alloy
An interpretation of the kinetics of martensitic transformation in a Ni45Co5Mn36.5In13.5 alloy
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DOI：
10.1016/j.actamat.2014.08.018
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发表时间：
2014-12
期刊：
影响因子：
9.4
通讯作者：
T. Fukuda;T. Kakeshita;Yong-hee Lee
中科院分区：
文献类型：
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作者：
T. Fukuda;T. Kakeshita;Yong-hee Lee
研究了Ni45Co5Mn36.5In13.5合金的马氏体相变动力学。该合金的MT起始温度Ms值随外加磁场的增加而逐渐降低，直到1.5T，Ms值在2T以下消失。在此磁场下，MT的时间-温度转变(TTT)曲线呈现清晰的C曲线。为了了解这一行为，我们通过测量合金的比热来评估母相和马氏体相的自由能Δ的差异。我们发现，随着磁场的增加，M_s大大偏离平衡温度T_0。我们还发现，Δ门槛MS随着MS的减少而增加。利用Δ的计算结果和马氏体形核的热激活模型，计算了不同磁场强度下的TTT图，并与实验结果进行了比较。我们估计热激活团簇的大小为(5 Nm)3，这可能被认为是马氏体核。
We investigated the kinetics of martensitic transformation (MT) using a Ni45Co5Mn36.5In13.5alloy. The MT start temperatureMsof this alloy decreases gradually with increasing applied magnetic field up to 1.5 T, andMsvanishes under 2 T. Under this magnetic field, the MT shows a clear C-curve in the time–temperature transformation (TTT) diagram. To understand this behavior, we evaluated the difference in the free energy Δgof the parent phase and the martensite phase by measuring the specific heat of the alloy. We found thatMslargely deviates from the equilibrium temperatureT0as the magnetic field increases. We also found that ΔgatMsincreases asMsdecreases. Using Δgthus evaluated and a thermal activation model for the nucleation of martensite, we calculated the TTT diagram for various magnetic field strengths so as to reproduce the experimentally obtained one. We estimated the size of the thermally activated cluster, which may be regarded as the nuclei of martensite, to be (5 nm)3.