Effect of Ni on microstructure and mechanical properties of Al?Mg?Si alloy for laser powder bed fusion
The microstructures and mechanical properties were systematically studied for the high-strength Al−5Mg2Si−1.5Ni alloy fabricated by laser powder bed fusion (L-PBF). It is found that the introduction of Ni (1.5 wt.％) into an Al−5Mg2Si alloy can significantly improve the L-PBF processibility and provide remarkable improvement in mechanical properties. The solidification range of just 85.5 K and the typical Al−Al3Ni eutectics could be obtained in the Ni-modified Al−5Mg2Si samples with a high relative density of 99.8％ at the volumetric energy density of 107.4 J/mm3. Additionally,the refined hierarchical microstructure was mainly characterized by heterogeneous α-Al matrix grains (14.6 μm) that contain the interaction between dislocations and Al−Al3Ni eutectics as well as Mg2Si particles. Through synergetic effects of grain refinement,dislocation strengthening and precipitation strengthening induced by Ni addition,the L-PBFed Al−5Mg2Si−1.5Ni alloy achieved superior mechanical properties,which included the yield strength of (425±15) Mpa,the ultimate tensile strength of (541±11) Mpa and the elongation of (6.2±0.2)％.
laser powder bed fusionAl−Mg−Si alloymicrostructural evolutionmechanical propertiesstrengthening mechanism
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