The objective of this work is to demonstrate that the mechanical response of multiphase materials is fundamentally different in an imposed deformation field that is homogeneous, versus in an imposed deformation field that is heterogeneous, at a length-scale greater than the microstructural length-scale. To this end, we focus on two dual-phase steels with significantly different nominal chemical composition and microstructure. The mechanical response of the steels is characterized by in-situ SEM tensile tests of flat dog-bone and single-edge notch specimens. The experimental results show that the dog-bone specimens of the two steels exhibit very similar mechanical response but the mechanical response of their single-edge notch specimens differs significantly. This is in contrast to any classical analysis that will predict the same mechanical response in the presence of a notch for two materials that give the same mechanical response under uniaxial tension. The high resolution in-situ tests coupled with microstructure-based digital image correlation and finite element analysis are then used to elucidate how the interlacing of imposed heterogeneous deformation field and material microstructure affects the mechanical response of these steels. Our results clearly highlight that a mechanistic analysis of multiphase materials under imposed heterogeneous deformation field must involve explicit consideration of the length-scales associated with the material microstructure.

这项工作的目的是证明，在大于微观结构长度尺度的长度尺度上，多相材料的机械响应在均质的施加变形场中与在异质的施加变形场中根本不同。为此，我们重点研究两种标称化学成分和微观结构明显不同的双相钢。钢材的机械响应通过扁平狗骨头和单边缘缺口样品的原位SEM拉伸测试来表征。实验结果表明，两种钢的狗骨试样表现出非常相似的机械响应，但是它们的单边缺口试样的机械响应却存在显着差异。这与任何经典分析相反，任何经典分析都将在存在缺口的情况下预测两种材料的机械响应，该两种材料在单轴张力下会给出相同的机械响应。然后使用高分辨率的原位测试以及基于微结构的数字图像相关性和有限元分析来阐明施加的异质形变场和材料微结构的交织如何影响这些钢的机械响应。我们的结果清楚地表明，在施加的非均匀变形场下对多相材料进行的机械分析必须涉及与材料微观结构相关的长度尺度的明确考虑。然后使用高分辨率的原位测试以及基于微结构的数字图像相关性和有限元分析来阐明施加的异质形变场和材料微结构的交织如何影响这些钢的机械响应。我们的结果清楚地表明，在施加的非均匀变形场下对多相材料进行的机械分析必须涉及与材料微观结构相关的长度尺度的明确考虑。然后使用高分辨率的原位测试以及基于微结构的数字图像相关性和有限元分析来阐明施加的异质形变场和材料微结构的交织如何影响这些钢的机械响应。我们的结果清楚地表明，在施加的非均质变形场下对多相材料进行的机械分析必须涉及与材料微观结构相关的长度尺度的明确考虑。