激光选区熔化工艺及热处理对稀土改性Al-Mn合金性能的影响

Effect of Selective Laser Melted Process and Heat Treatment on the Properties of Rare Earth Modified Al-Mn Alloy

分析了激光选区熔化(SLM)成形不同工艺参数对稀土改性Al-Mn合金致密度的影响,从而得到最佳工艺参数,在此基础上研究热处理工艺对SLM成形Al-Mn-Sc-Zr合金力学性能的影响。结果表明,过高的激光能量密度造成元素气化,使得成形件内部产生残余球形孔洞,过低的能量密度引起搭接不良,使得成形件内部形成不规则孔洞。将能量密度优化为52.6J/mm^(3)时,成形件内部缺陷减少,成形致密度提高至99.8%。SLM成形Al-Mn-Sc-Zr合金熔池内呈现两种不同的晶粒形态,熔池底部为等轴晶,而熔池中心为柱状晶。热处理之后,合金拉伸性能和显微硬度明显提升。经300℃保温4h后,Al-Mn-Sc-Zr合金获得优异的拉伸性能,其抗拉强度可达576MPa,且伸长率为11%。沉积态Al-Mn-Sc-Zr合金的显微硬度为131.2HV_(0.2),经280℃保温6h后,显微硬度(HV_(0.2))可提高至178.3。

The effects of different selective laser melting(SLM)parameters on relative density of SLM-processed rare earth modified Al-Mn alloy were investigated and the optimum parameters were presented.On this basis,the influence of heat treatment on mechanical properties of SLM-formed Al-Mn-Sc-Zr alloy was explored.The results indicate that a excessive applied laser energy density(E)leads to the spherical pores inclusion inside,which is attributed to the constituent evaporation.A low Eresults in the limited overlap ratio,leading to the formation of irregular pores.When Eis optimized to 52.6J/mm^(3),the internal defects of SLM-processed parts are reduced with improved densification level of 99.8%.Two kinds of grain morphology can be observed in the molten pool:equiaxed grains generated at the bottom and columnar grains at the center.Tensile properties and micro-hardness of the alloy can be improved effectively by heat treatment.After annealing at 300℃ for 4h,specimens exhibit excellent tensile properties,where tensile strength reaches 756MPa and elonagation is 11%.The micro-hardness of the as-deposited specimens are 131.2HV_(0.2)whereas that annealed at 280℃for 6his 178.3HV_(0.2).