Multi-stage martensitic transformation behaviors and microstructural characteristics of Ti-Ni-Hf high temperature shape memory alloy powders
Multi-stage martensitic transformation behaviors and microstructural characteristics of Ti-Ni-Hf high temperature shape memory alloy powders
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Ti-Ni-Hf高温形状记忆合金粉末多阶段马氏体相变行为及显微组织特征
DOI：
10.1016/j.jallcom.2018.12.064
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发表时间：
2019
影响因子：
6.2
通讯作者：
Zhao Liancheng
中科院分区：
文献类型：
--
作者：
Yi Xiaoyang;Meng Xianglong;Cai Wei;Zhao Liancheng
在Ti-49 Ni-15 Hf（at.%）合金中观察到异常的多阶段马氏体相变。等离子旋转电极法制备的合金粉末，其在很大程度上取决于颗粒尺寸。在加热和冷却过程中，粒径小于75 μm的Ti-Ni-Hf合金粉末和粒径为75 ~ 150 μm的Ti-Ni-Hf合金粉末分别发生两阶段和三阶段马氏体相变。在快速凝固过程中，由于较大的冷却速率和Hf的挣扎扩散速率，在离（Ti，Hf）2Ni析出相不同距离处Hf浓度存在显著差异，这是直径小于75 μm的Ti-Ni-Hf合金粉末发生两步马氏体相变的主要原因。除了在微观水平上的化学组成的变化，外层和内部之间的较大的合金粉末的独特的冷却速率导致的（Ti，Hf）2Ni沉淀物的量的差异，进一步导致在区分化学组成和外观的额外的马氏体相变。
An abnormal multi-stage martensitic transformation was observed in the Ti-49Ni-15Hf (at.%) alloy powders fabricated by the plasma rotating electrode process, which were largely dependent on the particle size. Upon heating and cooling process, the Ti-Ni-Hf alloy powders less than 75 μm and with the size of 75∼150 μm exhibited the two-stage and the three-stage martensitic transformation, respectively. During the rapid solidification, the significant variation of the Hf concentrations existed at the different distances from the (Ti,Hf)2Ni precipitates as a consequence of the larger cooling rate and the struggle diffusion rate of Hf, which was the main reason for the two-step martensite transformation in the Ti-Ni-Hf alloy powders smaller than 75 μm. In addition to the variation of the chemical composition at the micro-levels, the distinctive cooling rate between the outer layer and interior for the larger alloy powders led to the difference in the amounts of (Ti,Hf)2Ni precipitates, further resulting in the distinguishing chemical composition and the appearance of an additional martensitic transformation.