Local thermal expansions and lattice strains in Elinvar and stainless steel alloys
Local thermal expansions and lattice strains in Elinvar and stainless steel alloys
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DOI：
10.1103/physrevmaterials.2.023601
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发表时间：
2018-02
影响因子：
3.4
通讯作者：
T. Yokoyama;A. Koide;Y. Uemura
中科院分区：
文献类型：
--
作者：
T. Yokoyama;A. Koide;Y. Uemura
采用随温度变化的Cr、Fe和Ni边扩展X射线吸收精细结构（EXAFS）测量，结合路径积分有效经典势蒙特卡罗（PIECP MC）理论模拟，研究了Elinvar合金（Ni Span C）和不锈钢（AISI 304）的局部热膨胀和晶格应变.从埃林瓦合金的EXAFS分析，发现Fe周围的局部热膨胀比Ni和Cr周围的热膨胀小得多。这一观察结果可以简单地理解，因为埃林瓦合金中的Fe表现出不完全的类因瓦效应。此外，在Elinvar和SUS 304合金中，发现Cr周围的局部热膨胀和晶格应变大于Fe和Ni周围的那些。从两种合金的PIECP MC模拟，第一近邻Cr-Fe对显示出非常大的热膨胀，而Cr-Cr对显示出相当小的甚至负的热膨胀。因此，这些发现表明Elinvar和SUS 304合金中的晶格应变主要集中在Cr原子上。虽然铬在不锈钢中的作用是通过形成表面氧化铬来抑制腐蚀，但有趣的是，目前的研究表明，体相中的铬原子在吸收合金中不可避免的晶格应变方面发挥着隐藏的新作用。
Local thermal expansions and lattice strains in the Elinvar alloy(Ni Span C) and the stainless steel(AISI304) were investigated by the temperature-dependent Cr, Fe, and Ni-edge extended x-ray absorption fine-structure (EXAFS) measurements, combined with the path-integral effective classical potential Monte Carlo (PIECP MC) theoretical simulations. From the EXAFS analysis of the Elinvar alloy, the local thermal expansion around Fe is found to be considerably smaller than the ones around Ni and Cr. This observation can be understood simply because Fe in the Elinvar alloy exhibit an incomplete Invar-like effect. Moreover, in both the Elinvar and SUS304 alloys, the local thermal expansions and the lattice strains around Cr are found to be larger than those around Fe and Ni. From the PIECP MC simulations of both the alloys, the first-nearest neighbor Cr-Fe pair shows extraordinarily large thermal expansion, while the Cr-Cr pair exhibits quite small or even negative thermal expansion. These findings consequently indicate that the lattice strains in both the Elinvar and SUS304 alloys are concentrated predominantly on the Cr atoms. Although the role of Cr in stainless steel has been known to inhibit corrosion by the formation of surface chromium oxide, the present investigation may interestingly suggest that the Cr atoms in the bulk play a hidden new role of absorbing inevitable lattice strains in the alloys.