Matrix switch related to microstructural connectivity and its effect on strength in metals with duplex microstructure
Matrix switch related to microstructural connectivity and its effect on strength in metals with duplex microstructure
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与微观结构连通性相关的矩阵开关及其对双相微观结构金属强度的影响
DOI：
10.1016/j.msea.2017.03.002
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Takaki Setsuo
中科院分区：
文献类型：
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作者：
Nakada Nobuo;Kawasaki Shouhei;Kogakura Yuuki;Tsuchiyama Toshihiro;Takaki Setsuo
为了理解在介观尺度上对具有双重显微组织的金属的机械性能起主导作用的显微组织因素，在显微组织连通性方面研究了具有由软奥氏体和硬奥氏体组成的双重显微组织的Fe-Ni奥氏体合金的0.2%屈服应力作为硬奥氏体分数的函数的变化。0.2%屈服应力随硬奥氏体含量的增加而不断增加。但当硬奥氏体含量超过某一临界值时，强化行为发生变化，临界含量下的0.2%屈服应力由割线法计算的下限应力变为上限应力。这表明，在临界分数下，双相组织的基体由软奥氏体转变为硬奥氏体。另一方面，也证实了非单调强化行为与硬质奥氏体的显微组织连通性，即逾渗现象有很好的相关性。结果表明，割线法在考虑软、硬两相基体转换的情况下，可以较全面地预测双相组织金属的强度，而渗流指数有可能成为区分双相组织基体软、硬两相的有用参数，尽管需要进一步研究硬相连接的程度。
To understand the microstructural factors dominantly affecting the mechanical properties of metals with duplex microstructures on a mesoscale, the change in the 0.2% proof stress as a function of the hard austenite fraction of an Fe–Ni austenitic alloy having a duplex microstructure composed of soft and hard austenite was investigated in terms of the microstructural connectivity. The 0.2% proof stress continuously increased with increasing fraction of the hard austenite. However, the strengthening behavior changed when the hard austenite fraction exceeded a critical value; the 0.2% proof stress shifted from the lower limit stress to the upper limit one calculated by secant method at the critical fraction. This demonstrates that the matrix of duplex microstructure was switched from soft austenite to hard austenite at the critical fraction. On the other hand, it was also confirmed that the non-monotonic strengthening behavior has a good correlation with the microstructural connectivity of the hard austenite, that is, the percolation phenomenon. From these result, it was concluded that the strength of metals with duplex microstructure can be wholly predicted based on secant method while taking into account the matrix switching between soft and hard phases, and the percolation index has a possibility to be a useful parameter to distinguish between soft and hard phases which is the matrix of the duplex microstructure, although further investigation is needed on a degree of the hard phase connection.