Abstract In this study, several Mg-9%Al-2%Ca alloy round-bar specimens were fabricated by the selective laser melting (SLM) process. A fraction of the specimens was submitted to tensile testing. Then, the remaining fraction of specimens were drilled and subsequently submitted to further tensile testing interrupted at 90% of the ultimate tensile strength (UTS). Fracture surfaces were analyzed and an Electron Backscatter Diffraction (EBSD) analysis was performed to observe plastic strain. The results showed a dispersed plastic strain distribution that concentrated at the coarse grain microstructure, specifically at the outer regions of each melt pool formation. Microstructure coarsening is an intrinsic phenomenon of the SLM processes and induces crack arrest during the transition from a stable fracture to an unstable fracture. Accordingly, fractography results showed a large flattened area in the fracture surface, which suggests a stable and propagating plastic strain beneath the fracture surface, but no crack propagation of the corresponding length was found, despite interrupting the test at 90% of the UTS value. Based on this information, an indicator that evaluates plastic strain as continuous or discontinuous could be used in order to explain the high tensile strength and fracture behavior of SLM products in as-built conditions, which have been discussed but not verified to date.

中文翻译：

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选择性激光熔化制备不燃镁制品断裂过程中整个微观结构二元性的塑性应变分布

摘要 在本研究中，采用选择性激光熔化（SLM）工艺制备了多个 Mg-9%Al-2%Ca 合金圆棒试样。一部分试样进行拉伸试验。然后，对剩余部分的试样进行钻孔，随后进行进一步的拉伸测试，在 90% 的极限拉伸强度 (UTS) 下中断。分析断裂表面并进行电子背散射衍射 (EBSD) 分析以观察塑性应变。结果表明分散的塑性应变分布集中在粗晶粒微观结构，特别是在每个熔池形成的外部区域。显微组织粗化是 SLM 过程的固有现象，并在从稳定断裂到不稳定断裂的过渡过程中引起裂纹停止。因此，断口分析结果显示断裂表面有一个大的平坦区域，这表明断裂表面下方存在稳定和传播的塑性应变，但没有发现相应长度的裂纹扩展，尽管在 90% 的 UTS 值时中断了测试。基于此信息，可以使用将塑性应变评估为连续或不连续的指标来解释 SLM 产品在竣工条件下的高拉伸强度和断裂行为，这些问题已经讨论过但迄今为止尚未得到验证。