AISI 304 steel experiences plastic flow instability during tension at room temperature if appropriate conditions are applied: a low strain rate and a sufficiently long gauge section of the sample. Then, propagation of the strain-localised band is activated. The electron backscattered diffraction (EBSD) research revealed that the reason is not only the difference in the content of the secondary phase – martensite α’ across the front face, but also the change in the volume fraction of austenite grains with Copper (Cu) and Goss-Brass (GB) orientation. Consequently, there is a division between two areas of high and limited deformation capacity. The tendency to maintain the continuity of deformation fields induces a massive rotation of austenite grains to Cu and GB orientations, which then undergo shearing and phase transformation. As a result, momentary strain accumulation leaves behind a stiffer zone. It is shown that the trapping of austenite grains prone to large deformations, inside the matrix with Cu and GB orientations, makes the formation of a plastic strain front possible. These features improve the ductility and strength of the 304 steel over 316L and 316LN at room temperature. The in-situ EBSD tension studies for the considered grades reveal three developing textures, with their comparison showing a gradual decrease in the preferences of the Cu and GB components. Thus, the appearing bands of the accumulated strains in 316L are limited by the Cu and GB areas, while such blockages do not occur in 316LN. The presented strengthening mechanism is confirmed by the digital image correlation (DIC) measurements. The root-mean-square (RMS) function of strains along the tensile direction, characterising the linear surroundings of the considered point, is introduced as a tool for linking the micro and macro scales. The experimental results provide a basis for explaining discontinuous front propagation at a temperature near 0 K.

中文翻译：

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奥氏体不锈钢在室温下塑性流动的不稳定性：宏观测试和微观结构分析


如果应用适当的条件，AISI 304 钢在室温下拉伸时会出现塑性流动不稳定：低应变率和样品足够长的规格部分。然后，菌株定位带的传播被激活。电子背散射衍射 （EBSD） 研究表明，原因不仅在于正面第二相马氏体 α' 含量的差异，还在于铜 （Cu） 和戈斯黄铜 （GB） 取向的奥氏体晶粒体积分数的变化。因此，存在两个变形能力高和有限的区域。保持变形场连续性的趋势导致奥氏体晶粒向 Cu 和 GB 取向的大规模旋转，然后发生剪切和相变。因此，瞬时应变累积会留下一个更坚硬的区域。结果表明，在具有 Cu 和 GB 取向的基体内部捕获容易发生大变形的奥氏体晶粒，使得形成塑性应变前沿成为可能。这些特性在室温下提高了 304 钢的延展性和强度，优于 316L 和 316LN。所考虑等级的原位 EBSD 张力研究揭示了三种发展中的织构，它们的比较显示 Cu 和 GB 组分的偏好逐渐降低。因此，316L 中积累菌株的出现条带受 Cu 和 GB 区域的限制，而这种阻塞在 316LN 中不会发生。所提出的增强机制通过数字图像相关 （DIC） 测量得到证实。 沿拉伸方向的应变均方根 （RMS） 函数，表征所考虑点的线性环境，作为连接微观和宏观尺度的工具引入。实验结果为解释在接近 0 K 的温度下的不连续前沿传播提供了基础。