Aging-induced two-stage reverse martensitic transformation behavior in Co46Ni27Ga27 high-temperature shape memory alloy
Aging-induced two-stage reverse martensitic transformation behavior in Co46Ni27Ga27 high-temperature shape memory alloy
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DOI：
10.1007/s12598-011-0424-0
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发表时间：
2011-10
期刊：
影响因子：
8.8
通讯作者：
D. Su;Yan Li;Y. Xin;B. Yuan
中科院分区：
文献类型：
--
作者：
D. Su;Yan Li;Y. Xin;B. Yuan
利用光学显微镜（OM）、透射电镜（TEM）、X射线衍射分析（XRD）和差示扫描量热仪（DSC）研究了823 K奥氏体时效对CoNiGa合金显微组织和马氏体相变行为的影响。显微组织观察结果表明，未时效态CoNiGa合金由四方非调制马氏体和面心立方γ相组成。结果表明，在奥氏体时效过程中，析出了一种新的纳米尺寸的面心立方相，并在析出相周围形成亚稳的时效马氏体。时效2 h和24 h的试样由于时效马氏体与原始马氏体的成分差异，发生了两阶段逆马氏体相变。对于时效120 h的CoNiGa合金，由于亚稳时效马氏体的消失和原始马氏体相变潜热的减小，没有发现逆相变。随着时效时间的延长，CoNiGa合金的马氏体相变温度降低。
The effect of austenite aging at 823 K on the microstructures and martensitic transformation behavior of CoNiGa alloy has been investigated using optical microscopy (OM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and differential scanning calorimeter (DSC). The microstructure observation results show that the unaged CoNiGa alloy is composed of the tetragonal nonmodulated martensite phase and face-centered cubic γ phase. It is found that a new nanosized fcc phase precipitates in the process of austenite aging, leading to the formation of metastable age-affected martensite around the precipitates with composition inhomogeneity. Two-stage reverse martensitic transformation occurs in the samples aged for 2 and 24 h due to the composition difference between the age-affected martensite and the original martensite. For the CoNiGa alloy aged for 120 h, no reverse transformation can be detected due to the disappearance of the metastable age-affected martensite and the small latent heat of the original martensite. The martensitic transformation temperatures of the CoNiGa alloy decrease with an increase in aging time.