Grain size dependence of Young's modulus and hardness for nanocrystalline NiTi shape memory alloy
Grain size dependence of Young's modulus and hardness for nanocrystalline NiTi shape memory alloy
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纳米晶 NiTi 形状记忆合金杨氏模量和硬度的晶粒尺寸依赖性
DOI：
10.1016/j.matlet.2017.10.024
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发表时间：
2018
影响因子：
3
通讯作者：
Sun Qingping
中科院分区：
文献类型：
--
作者：
Xia Minglu;Liu Pan;Sun Qingping
本文通过实验研究了纳米晶NiTi形状记忆合金的杨氏模量和硬度随晶粒尺寸的变化规律。采用冷轧法制备了含有纳米晶碎片的非晶NiTi合金，并通过退火处理得到了晶粒尺寸为10 ~ 120 nm的多晶NiTi合金。采用宏观等温拉伸和微观纳米压痕法对纳米晶NiTi的杨氏模量和硬度进行了定量研究。结果表明，纳米晶NiTi的杨氏模量随GS的增加先减小（GS < 62 nm）后增大（GS > 62 nm）。杨氏模量的非单调GS依赖性源于材料中奥氏体、马氏体和非晶相的晶粒尺寸和体积分数的综合影响。随着GS的增加，纳米晶NiTi的硬度单调下降，这是由于降低了名义相变应力和塑性屈服应力。这种硬度的GS依赖性可用于通过纳米压痕硬度测试快速测定纳米晶NiTi中的GS。
In this paper,grain size(GS) dependence of Young’s modulus and hardness for nanocrystalline NiTi shape memory alloy is investigated by experiments. Amorphous NiTi with nanocrystalline debris is fabricated via cold-rolling and polycrystalline NiTi with average GS from 10 nm to 120 nm is obtained by subsequent annealing. Young’s modulus and hardness of nanocrystalline NiTi are quantified by macroscopic isothermal tension and microscopic nanoindentation. It is shown that Young’s modulus of nanocrystalline NiTi first decreases (for GS < 62 nm) and then increases (for GS > 62 nm) with GS in the nano-scale region. The non-monotonic GS dependence of Young’s modulus originates from the combined effects of grain size and volume fractions of austenite, martensite and amorphous phase in the material. It is also shown that with the increase of GS up to 120 nm, hardness of nanocrystalline NiTi monotonically decreases due to the reduced nominal phase transition stress and plastic yielding stress. Such GS dependence of hardness can be utilized for rapid determination of GS in nanocrystalline NiTi via nanoindentation hardness test.