The focus of this study is on the characterization of the local plastic deformation and failure of functionally graded 22MnB5 plates after hot stamping using an in situ approach. Various forming strategies at elevated temperatures are performed using differentially tempered forming tools to locally tailor the microstructure. By controlling the cooling rate, graded as well as martensitic and ferritic–pearlitic microstructures are obtained. Experimental analysis includes evaluation of the material- and geometry-dependent local strain evolution by tensile tests coupled with digital image correlation conducted on two different sample geometries, tapered and nontapered. Experimental results reveal a much more complex deformation behavior for the functionally graded than for homogenous samples. As expected, the distribution of plastic strain of the graded sample is depending on the mixture of its constituting microstructures; however, different types of localized failure after necking are found. Obviously, failure evolution also depends on the sample geometry. Failure patterns observed include shear bands, crossed bands, or homogenous localization of strain, i.e., traditional necking. Eventually, in the case of the nontapered geometry, a lower level of local plastic strain with multiple necking sites is observed. Based on findings presented, detailed process-microstructure-property-damage relationships are established.

中文翻译：

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功能梯度 22MnB5 钢的力学性能、宏观变形行为和显微组织表征

本研究的重点是使用原位方法对功能梯度 22MnB5 板在热冲压后的局部塑性变形和失效进行表征。使用不同回火成形工具在高温下执行各种成形策略以局部调整微观结构。通过控制冷却速度，可以获得梯度以及马氏体和铁素体-珠光体显微组织。实验分析包括通过拉伸试验评估与材料和几何形状相关的局部应变演变，并在两个不同的样品几何形状（锥形和非锥形）上进行数字图像相关。实验结果表明，功能分级的变形行为比均质样品复杂得多。正如预期的那样，梯度样品的塑性应变分布取决于其构成微观结构的混合物；然而，在颈缩后发现了不同类型的局部失效。显然，故障演变也取决于样品几何形状。观察到的失效模式包括剪切带、交叉带或应变的均匀定位，即传统的颈缩。最终，在非锥形几何形状的情况下，观察到具有多个颈缩部位的较低水平的局部塑性应变。根据所提供的研究结果，建立了详细的工艺-微观结构-性能-损坏关系。观察到的失效模式包括剪切带、交叉带或应变的均匀定位，即传统的颈缩。最终，在非锥形几何形状的情况下，观察到具有多个颈缩部位的较低水平的局部塑性应变。根据所提供的研究结果，建立了详细的工艺-微观结构-性能-损坏关系。观察到的失效模式包括剪切带、交叉带或应变的均匀定位，即传统的颈缩。最终，在非锥形几何形状的情况下，观察到具有多个颈缩部位的较低水平的局部塑性应变。根据所提供的研究结果，建立了详细的工艺-微观结构-性能-损坏关系。