Additively manufactured metallic materials exhibit excellent mechanical strength. However, they often fail prematurely owing to external defects (pores and unmelted particles) that act as sites for crack initiation. Cracks then propagate through grain boundaries and/or cellular boundaries that contain continuous brittle second phases. In this work, the premature failure mechanisms in selective laser melted (SLM) materials were studied. A submicron structure was introduced in a SLM Ag–Cu–Ge alloy that showed semicoherent precipitates distributed in a discontinuous but periodic fashion along the cellular boundaries. This structure led to a remarkable strength of 410 ± 3 MPa with 16 ± 0.5% uniform elongation, well surpassing the strength-ductility combination of their cast and annealed counterparts. The hierarchical SLM microstructure with a periodic arrangement of precipitates and a high density of internal defects led to a high strain hardening rate and strong strengthening, as evidenced by the fact that the precipitates were twinned and encircled by a high density of internal defects, such as dislocations, stacking faults and twins. However, the samples fractured before necking owing to the crack acceleration along the external defects. This work provides an approach for additively manufacturing materials with an ultrahigh strength combined with a high ductility provided that premature failure is alleviated.

增材制造的金属材料具有出色的机械强度。但是，由于外部缺陷（孔和未融化的颗粒）会引起裂纹萌生，它们通常会过早失效。然后，裂纹通过包含连续的脆性第二相的晶界和/或晶胞边界传播。在这项工作中，研究了选择性激光熔融（SLM）材料中的过早失效机理。在SLM Ag-Cu-Ge合金中引入了亚微米结构，该结构显示出半连续沉淀沿细胞边界以不连续但周期性的方式分布。这种结构产生了410±3 MPa的卓越强度，具有16±0.5％的均匀伸长率，远远超过了铸件和退火件的强度-延展性组合。具有析出物周期性排列和内部缺陷的高密度的分层SLM微结构导致高应变硬化速率和强强化，这一事实证明了析出物被诸如内部密度之类的高密度内部孪晶缠绕和包围错位，堆垛层错和双胞胎。然而，由于沿着外部缺陷的裂纹加速，样品在颈缩之前破裂。这项工作提供了一种方法，该方法可以减轻过早的破坏，并具有超高强度和高延展性的增材制造技术。事实证明，析出物被高密度的内部缺陷（例如位错，堆垛层错和孪晶）缠结并包围。然而，由于沿着外部缺陷的裂纹加速，样品在颈缩之前破裂。这项工作提供了一种方法，该方法可以减轻过早的破坏，并具有超高强度和高延展性的增材制造技术。事实证明，析出物被高密度的内部缺陷（例如位错，堆垛层错和孪晶）缠绕并包围。然而，由于沿着外部缺陷的裂纹加速，样品在颈缩之前破裂。这项工作提供了一种方法，该方法可以减轻过早的破坏，并具有超高强度和高延展性的增材制造技术。