Nanostructured metallic materials with abundant high-angle grain boundaries exhibit high strength and good radiation resistance. While the nanoscale grains induce high strength, they also degrade tensile ductility. We show that a gradient nanostructured ferritic steel exhibits simultaneous improvement in yield strength by 36% and uniform elongation by 50% compared to the homogenously structured counterpart. In situ tension studies coupled with electron backscattered diffraction analyses reveal intricate coordinated deformation mechanisms in the gradient structures. The outermost nanolaminate grains sustain a substantial plastic strain via a profound deformation mechanism involving prominent grain reorientation. This synergistic plastic co-deformation process alters the rupture mode in the post-necking regime, thus delaying the onset of fracture. The present discovery highlights the intrinsic plasticity of nanolaminate grains and their significance in simultaneous improvement of strength and tensile ductility of structural metallic materials.

中文翻译：

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具有优异拉伸塑性的梯度纳米结构钢

具有丰富的大角度晶界的纳米结构金属材料表现出高强度和良好的耐辐射性。虽然纳米级晶粒具有高强度，但它们也会降低拉伸延展性。我们发现，与均质结构的对应钢相比，梯度纳米结构铁素体钢的屈服强度同时提高了 36%，均匀伸长率提高了 50%。原位张力研究与电子背散射衍射分析相结合揭示了梯度结构中复杂的协调变形机制。最外层的纳米层压晶粒通过涉及显着晶粒重新取向的深刻变形机制来维持显着的塑性应变。这种协同塑性共同变形过程改变了颈缩后的断裂模式，从而延迟了断裂的发生。本发现强调了纳米层压晶粒的固有塑性及其在同时提高结构金属材料的强度和拉伸延展性方面的重要性。