Abstract
? 2022 Elsevier B.V.The response of heat-treatment of an Al-5Mg2Si-2Mg alloy fabricated by laser assisted powder bed fusion (LPBF) was investigated for microstructural evolution and mechanical properties. The results showed that the as-LPBFed Al-5Mg2Si-2Mg alloy was featured by the refined compact Al-cells and the divorced Mg2Si eutectic network. After solution at 490 oC for 1 h, the Mg2Si eutectics were broken to form coarse Mg2Si particles. On the contrary, the characteristics of as-aged microstructure included the heritage of Al-cells and divorced Mg2Si eutectics, and the newly formed ultrafine in-situ Mg2Si particles in the matrix. Tensile results indicated that solution with and without subsequent ageing are not effective for strength improvement. The relative density, yield strength and ultimate tensile strength (UTS) of as-LPBFed alloy decreased obviously from 99.25 %, 295 MPa, and 453 MPa to 98.75 %, 167 MPa, and 292 MPa, respectively. On the other hand, the yield strength of 377 MPa, UTS of 488 MPa and elongation of 9.6 % can be achieved after direct ageing at 180 oC for 3.5 h, showing 28 % increase of yield strength in comparison with as-LPBFed alloy, but still with excellent ductility for engineering applications. It is found that the enhanced mechanical properties are mainly attributed to the newly formed ultrafine in-situ Mg2Si particles. From the results above, the direct ageing was found as a suitable heat treatment method capable of enhancing the strength of as-LPBFed Al-5Mg2Si-2Mg alloy.
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