ABSTRACT The mechanical behavior of multilayer steel structures fabricated via wire and arc additive manufacturing (WAAM) has been investigated from the multiscale perspective. The multimaterial WAAM approach can control a heterogeneous structure and improve its mechanical properties. In this study, WAAM equipment based on plasma arc welding was used to fabricate two pairs of single- and duplex-phase multilayer steel structures using austenitic and martensitic stainless steel wires. The heterogeneity of these structures was characterized through micro-indentation tests. In addition, tensile tests of the multilayer structures were conducted to evaluate the effect of heterogeneity on macroscopic material properties. The deformation behavior of the heterogeneous multilayer steel structures was investigated by comparison with the finite element simulations of tensile tests in which the finite element models were created according to the estimated local elastoplastic properties from the results of micro-indentation tests. The micro-indentation tests revealed that the local mechanical properties significantly change during WAAM in cases where martensitic stainless steel wire was used. Additionally, strain-induced transformation plasticity was particularly observed in duplex cases, caused by the metastable austenite phase formed according to the thermal history and through the mixing of alloy elements. Thus, the heterogeneity of the multilayer steel structures became more complicated than its design, and consequently, its macroscopic mechanical properties exceeded the upper and lower bounds of a micromechanic estimation. The results show the potential to fabricate a structure having a unique mechanical behavior via the multimaterial WAAM approach.

中文翻译：

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线材和电弧增材制造多层钢结构力学行为的多尺度分析

摘要 从多尺度角度研究了通过线材和电弧增材制造 (WAAM) 制造的多层钢结构的机械性能。多材料 WAAM 方法可以控制异质结构并改善其机械性能。在这项研究中，基于等离子弧焊的 WAAM 设备用于制造两对使用奥氏体和马氏体不锈钢丝的单相和双相多层钢结构。这些结构的异质性通过微压痕测试表征。此外，还进行了多层结构的拉伸试验，以评估异质性对宏观材料性能的影响。通过与拉伸试验的有限元模拟进行比较，研究了异质多层钢结构的变形行为，其中有限元模型是根据微压痕试验结果估计的局部弹塑性性能创建的。微压痕测试表明，在使用马氏体不锈钢丝的情况下，WAAM 期间局部机械性能会发生显着变化。此外，在双相情况下特别观察到应变诱导相变塑性，这是由根据热历史和合金元素混合形成的亚稳态奥氏体相引起的。因此，多层钢结构的异质性变得比其设计更复杂，因此，其宏观力学性能超出了微观力学估计的上限和下限。结果显示了通过多材料 WAAM 方法制造具有独特机械行为的结构的潜力。