激光增材制造6061铝合金热处理及强韧机理

Heat treatment and strengthening mechanisms of laser additive manufactured 6061 aluminum alloy

采用激光粉末床熔融(Laser powder bed fusion,LPBF)增材制造技术对6061铝合金进行制备成形。首先采用基板预热处理获得了无裂纹缺陷的打印试样,随后对打印合金进行热处理,并对比分析不同热处理工艺制度对合金组织性能的影响规律。结果表明,在直接打印(As printed,AP)状态下,合金元素以过饱和固溶体的形式存在于基体中,合金的抗拉强度仅为249 MPa。在固溶处理(Solution treatment,ST)+人工时效(Aging treatment,AT)和直接AT工艺下,铝合金的力学性能明显提升。其中,直接AT处理后,6061铝合金同时具备良好的强度和塑性,抗拉强度和伸长率分别为359 MPa和12.5%;而ST+AT处理后,合金强度升高至377 MPa,伸长率略有降低,为10.1%。AT处理有利于促进细针状Mg2 Si相在基体内弥散析出,通过析出强化效应,合金抗拉强度得到明显提高。

High strength 6061 aluminum alloy was printed by the laser powder bed fusion laser additive manufacturing technology.Firstly,the crack free 6061 aluminum alloy was obtained with the substrate preheating.And then,the printed alloys were heat treated,and the corresponding effect of heat treatments on the microstructure and mechanical properties was compared and analyzed.The results show that under the as printed(AP)condition,the alloy elements exist in the matrix in the form of supersaturated solution,and the tensile strength of the alloy is only 249 MPa.In the solution treatment(ST)+aging treatment(AT)and direct manual AT process,the mechanical properties of the aluminum alloy are significantly improved.After direct AT treatment,the alloy has high tensile strength and fraction elongation,359 MPa and 12.5%,respectively.While after ST+AT,the alloy has a higher strength of 377 MPa and a lower elongation of 10.1%.The AT treatment is conducive to promoting the diffusion and precipitation of fine-needle Mg2 Si phase in the Al matrix,and the tensile strength of the alloy is significantly improved by the precipitate strengthening effect.