Effect of Ni on microstructure and mechanical properties of Al−Mg−Si alloy for laser powder bed fusion

Ni对激光粉末床熔融Al-Mg-Si合金显微组织及力学性能的影响

The microstructures and mechanical properties were systematically studied for the high-strength Al−5Mg_(2)Si−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−5Mg_(2)Si 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−5Mg_(2)Si samples with a high relative density of 99.8%at the volumetric energy density of 107.4 J/mm^(3).Additionally,the refined hierarchical microstructure was mainly characterized by heterogeneousα-Al matrix grains(14.6μm)that contain the interaction between dislocations and Al−Al3Ni eutectics as well as Mg_(2)Si particles.Through synergetic effects of grain refinement,dislocation strengthening and precipitation strengthening induced by Ni addition,the L-PBFed Al−5Mg_(2)Si−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)%.

对激光粉末床熔融(L-PBF)制备的高强Al-5Mg_(2)Si-1.5Ni合金的显微组织及力学性能进行系统研究。结果表明,在Al-5Mg_(2)Si合金中引入1.5%(质量分数)的Ni可以显著改善L-PBF成形性能并提升力学性能。当体积能量密度为107.4 J/mm^(3)时,Ni改性Al-5Mg_(2)Si合金的凝固区间仅为85.5 K,并且获得了典型的Al-Al3Ni共晶组织,合金相对密度达到99.8%。此外,细化的分层组织主要表现为平均尺寸为14.6μm的非均匀α-Al晶粒以及位错与Al-Al3Ni共晶和Mg_(2)Si间的交互作用。在Ni添加引起的晶粒细化、位错强化和析出强化协同作用下,L-PBF成形Al-5Mg_(2)Si-1.5Ni合金获得了优异的力学性能,其屈服强度为(425±15)MPa,极限抗拉强度为(541±11)MPa,伸长率为(6.2±0.2)%。