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Additives; Aluminum alloys; Biomechanics; Cracks; Electric arc welding; Grain boundaries; High strength alloys; Magnesium alloys; Melting; Nanoparticles; Scandium alloys; Selective laser melting; Silicon alloys; Stacking faults; Tensile strength; Textures, Aging conditions; Alloy compositions; Grain boundary strengthening; Refined microstructure; Selective laser melting (SLM); Solid solution strengthening; Strength and elongations; Strengthening mechanisms, Zircaloy
Abstract:
To develop high-strength Al alloys for selective laser melting (SLM) additive manufacturing, we designed a series of Al-Mg(-Si)-Sc-Zr alloys and additively manufactured them using atomized alloy powders. In the absence of Si, the developed Al-xMg-0.2Sc-0.1Zr (x = 1.5, 3.0 and 6.0 wt) alloys are all susceptible to hot cracking and the average crack density increases with increasing Mg content. The addition of 1.3 wt Si into the Al-6Mg-0.2Sc-0.1Zr alloys effectively inhibits hot cracking during SLM and simultaneously refines the microstructure, and thus leading to enhanced mechanical properties in the as-printed samples. By further fine-tuning the alloy compositions, we designed a new alloy Al-8.0Mg-1.3Si-0.5Mn-0.5Sc-0.3Zr. This new alloy demonstrates significantly refined microstructure consisting of submicron cells with coherent Al3(Sc,Zr) nano-particle (2–15 nm) residing in the cell and intergranular Al-Mg2Si eutectic (Mg2Si diameter 10–100 nm). High-density stacking faults and a unique 9R phase are formed in the as-printed sample. The tensile strength and elongation of the as-printed sample are up to 497 MPa and 11, respectively. After the aging treatment, the tensile strength reaches 550 MPa, while the ductility ranges from 8 to 17, depending on the aging conditions. In addition to solid solution strengthening, grain boundary strengthening and nanoparticle strengthening, the high-density stacking faults also contributes to strengthening. © 2020 Acta Materialia Inc.
