An AlSi3.5Mg2.5 (wt%) alloy with excellent mechanical properties was produced via laser powder bed fusion in this study. The yield strength, tensile strength, and elongation of this as-built AlSi3.5Mg2.5 alloy reach about 406 MPa, 501 MPa, and 8.6%, respectively. These properties are dramatically superior to the current additively manufactured Al-Si-Mg alloys. A direct-aging treatment at 170°C for one hour increases the yield strength and ductility further to about 417 MPa and 11.0%, respectively, with the tensile strength remaining the same level. The microstructures and strengthening mechanisms of the as-built and direct-aged samples were investigated systematically. The underlying micromechanical mechanisms of the as-built and direct-aged samples were examined based on a combination of in-situ synchrotron X-ray diffraction and three-dimensional crystal plasticity modeling. The as-built AlSi3.5Mg2.5 alloy possesses a fine microstructure, including fine grains and nano-sized Mg₂Si and Si precipitates. After direct-aging treatment, additional Mg₂Si and Si precipitate out. Besides, element diffusion upon aging treatment causes migration of cell boundaries and relaxation of residual stress. The direct-aging treatment leads to an increased Orowan strengthening, dislocation strengthening, and load-bearing strengthening effects. Moreover, the variations of microstructure and residual stress after the aging treatment change the dislocation behavior and increase the dislocation storage capacity, causing an increased ductility. Nevertheless, the aging treatment does not alert the type of damage and fracture. This study provides valuable insights to tailor the microstructure and mechanical properties of additively manufactured Al-Si-Mg alloys.

在本研究中，通过激光粉末床熔融制备了具有优异机械性能的 AlSi3.5Mg2.5 (wt%) 合金。这种建成后的 AlSi3.5Mg2.5 合金的屈服强度、抗拉强度和伸长率分别达到约 406 MPa、501 MPa 和 8.6%。这些性能显着优于当前的增材制造的 Al-Si-Mg 合金。在 170°C 下直接时效处理 1 小时后，屈服强度和延展性分别进一步提高到约 417 MPa 和 11.0%，而拉伸强度保持不变。系统地研究了建成和直接时效样品的微观结构和强化机制。基于原位同步加速器 X 射线衍射和三维晶体塑性建模的组合，研究了竣工和直接老化样品的基本微机械机制。建成后的 AlSi3.5Mg2.5 合金具有精细的微观结构，包括细晶粒和纳米尺寸的镁₂ Si和Si沉淀。在直接时效处理后，额外的Mg ₂ Si和Si析出。此外，时效处理时的元素扩散会导致单元边界的迁移和残余应力的松弛。直接时效处理导致 Orowan 强化、位错强化和承载强化效果增加。此外，时效处理后显微组织和残余应力的变化改变了位错行为，增加了位错存储能力，导致延展性增加。尽管如此，时效处理并不会提醒损坏和断裂的类型。这项研究为定制增材制造的 Al-Si-Mg 合金的微观结构和机械性能提供了宝贵的见解。