Abstract To further understand the internal residual stress that is microscopically generated via martensitic transformation in steels, the origin of internal strain attributed to Bain correspondence between face-centered cubic (fcc) and body-centered cubic (bcc) was evaluated from macro- and micro-viewpoints and its effect on hardness was investigated in an interstitial free Fe-16%Ni martensite. Neutron diffractometry and electron backscatter diffraction analysis showed that body-centered cubic (bcc) crystal structure of as-quenched martensite contained elastic distortions leading to small tetragonality, even in martensitic steels without solute carbon, and that the extended [001]bcc of martensite tended to be parallel to fcc of prior fcc austenite. In addition, the combination of micro-scale focused ion beam (FIB) and high-precision digital image correlation techniques revealed that a micropillar fabricated by FIB processing within a martensite block was anisotropically deformed by the release of the residual strain distributed in as-quenched martensite in correspondence with the tetragonal distortions of the bcc crystal structure. These results prove that a small part of the Bain strain remained as an internal elastic residual strain and was microscopically distributed among Bain groups in lath martensite after martensitic transformation. Furthermore, the residual strain generated a hydrostatic internal stress, and therefore, the nanohardness decreased considerably by the micropillar fabrication accompanied by the release of the internal stress. This means that the internal residual stress in martensite among Bain groups influences the mechanical properties of martensitic steel.

中文翻译：

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源自贝恩应变的内部残余应力及其对 Fe-Ni 马氏体硬度的影响

摘要 为进一步了解钢中马氏体相变在微观上产生的内部残余应力，从宏观和微观角度评估了面心立方（fcc）和体心立方（bcc）之间的贝恩对应引起的内部应变的起源。 - 观点及其对硬度的影响在无间隙的 Fe-16%Ni 马氏体中进行了研究。中子衍射和电子背散射衍射分析表明，即使在不含溶质碳的马氏体钢中，淬火马氏体的体心立方 (bcc) 晶体结构包含导致小四方性的弹性变形，并且马氏体的扩展 [001]bcc 趋于平行于先前 fcc 奥氏体的 fcc。此外，微尺度聚焦离子束 (FIB) 和高精度数字图像相关技术的结合表明，在马氏体块内通过 FIB 处理制造的微柱因分布在相应淬火马氏体中的残余应变的释放而发生各向异性变形与 bcc 晶体结构的四方扭曲。这些结果证明，一小部分贝恩应变保留为内弹性残余应变，并在马氏体相变后在板条马氏体中微观分布在贝恩组中。此外，残余应变产生静水内应力，因此，随着内应力的释放，微柱制造使纳米硬度显着降低。