Martensitic steels are widely used structural materials with outstanding mechanical properties. Their high strength is provided by the non-diffusional phase transformation of fcc g into thin lamellar bcc plates during fast cooling. Coherency strains between the fcc and bcc lamellae induce large dislocation densities in the range of 10¹⁶ m⁻², well above the densities attainable by conventional plastic deformation. Using high resolution X-ray line profile analysis, scanning electron microscopy, and hardness tests we show that during tensile deformation when the active Burgers vectors are within the lath plane the lath-packets work soften. On the contrary, when the active Burgers vectors are oblique to the lath-plane the lath-packets work harden. The softening and hardening processes in the differently oriented lath-packets produce a composite of hard and soft components on the length scale of lath-packet size. The stress–strain response of the alloy is discussed in terms of the different mean free paths and the different annihilation lengths of dislocations in the softened and hardened lath-packets. The relatively good ductility is shown to be produced by the composite microstructure induced by plastic strain.

中文翻译：

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变形引起的软硬板条包增强了马氏体钢的延展性

马氏体钢是具有优异机械性能的广泛使用的结构材料。它们的高强度是通过在快速冷却过程中将fcc g无扩散相转化为薄层状bcc板而提供的。fcc和bcc薄层之间的相干应变引起10 ¹⁶ m ^-2范围内的大位错密度，远高于传统塑性变形所能达到的密度。使用高分辨率X射线线轮廓分析，扫描电子显微镜和硬度测试，我们表明，在拉伸变形过程中，当主动Burgers向量位于板条平面内时，板条组会软化。相反，当有效的Burgers向量倾斜于板条平面时，板条包会变硬。在不同方向的板条包中的软化和硬化过程在板条包尺寸的长度尺度上产生硬组分和软组分的复合物。讨论了合金的应力-应变响应，其中包括在软化和硬化后的板条包中不同的平均自由程和不同的位错hil灭长度。