To enhance the fundamental understanding for micromechanical lath martensite deformation, the microstructure as well as macro- and microscopic tensile properties of as-quenched 15–5 PH stainless steel are systematically analysed depending on the austenitisation temperature. Based on electron backscatter diffraction (EBSD) and backscattered electron (BSE) analysis, it is noted that the martensite morphology alters from a less defined to a more clearly defined parallel arrangement of the block and lath structure with increasing temperature. For an in-depth quantification of the hierarchical boundary strengthening contributions in relation to local stress/strain heterogeneity, separate high-fidelity virtual microstructures are realised for the different scales (prior austenite grains, packets and blocks). This is consistent with the materials transformation process. The virtual microstructures are simulated employing the crystal plasticity finite element method (CPFEM) adapted for handling high dislocation density and encompassing all relevant strengthening mechanisms by boundaries, dislocations and solute atoms. While accurately capturing the measured size-dependent stress–strain behaviour, the simulations reveal in line with the experiments (Hall–Petch) that blocks are the most effective dislocation motion barrier, causing increased strain hardening and stress/strain heterogeneity. Furthermore, since strain localisation is predicted strongest in the distinct block structure, the experimentally observed early plastic material yielding is thought to be favoured here.

中文翻译：

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通过实验和基于位错密度的晶体塑性将应力/应变不均匀性与板条马氏体强度联系起来

为了增强对微机械板条马氏体变形的基本理解，根据奥氏体化温度，系统地分析了淬火 15-5 PH 不锈钢的显微组织以及宏观和微观拉伸性能。基于电子背散射衍射 (EBSD) 和背散射电子 (BSE) 分析，我们注意到，随着温度的升高，马氏体形态从块体和板条结构的不太明确的平行排列转变为更明确的平行排列。为了深入量化与局部应力/应变异质性相关的分级边界强化贡献，针对不同尺度（原奥氏体晶粒、包和块）实现了单独的高保真度虚拟微观结构。这与材料的转变过程是一致的。采用晶体塑性有限元法 (CPFEM) 模拟虚拟微观结构，该方法适用于处理高位错密度，并包含边界、位错和溶质原子的所有相关强化机制。在准确捕获测量的与尺寸相关的应力应变行为的同时，模拟显示与实验（Hall-Petch）一致，块是最有效的位错运动障碍，导致应变硬化和应力/应变异质性增加。此外，由于预测应变局部化在不同的块结构中最强，因此实验观察到的早期塑性材料屈服被认为在这里是有利的。