激光选区熔化成形AZ91D镁合金的力学性能与精度研究

Mechanical Properties and Accuracy of AZ91D Magnesium Alloy Processedby Selective Laser Melting

激光选区熔化(selective laser melting,SLM)增材制造技术可实现镁合金零件的快速制造,但有关SLM成形镁合金力学性能和成形精度的综合研究较少。以AZ91D镁合金为对象,研究了SLM成形镁合金的致密化行为、组织结构、力学性能、表面粗糙度和尺寸精度。结果表明:当实体填充所用的激光能量密度大于110 J/mm3时,成形试样可达到高度致密(致密度>99.5%),但致密度与激光能量密度并无严格的一一对应关系。高致密样品呈现微细枝晶状显微组织,极限抗拉强度、屈服强度、伸长率均超过同牌号压铸件。仅采用实体填充时,高致密、高性能样品的加工误差较小,为0.25%,但表面粗糙度较高,为(17.7±1.9)μm;加入适当的轮廓扫描后,可以将表面粗糙度降低至(14.4±1.1)μm,加工误差降低至0.12%。

Selective laser melting(SLM)additive manufacturing technology can realize the rapid forming of magnesium alloy parts.However,comprehensive researches on mechanical properties and forming accuracy of magnesium alloy fabricated by SLM are limited.The densification behavior,microstructure,mechanical properties,surface roughness and dimensional accuracy of SLM-fabricated AZ91D magnesium alloy were investigated.The results show that the SLM-fabricated samples achieve high relative density(>99.5%)when the laser energy density for solid filling exceeds 110 J/mm3.However,there is no strict one-to-one correlation between relative density and laser energy density.The high relative density sample has fine dendritic microstructure and the ultimate tensile strength,yield strength and elongation all surpass those of the die-casting counterparts.The processing error of the high density and high performance sample is 0.25%when only employing solid filling strategy,but the surface roughness is as high as(17.7±1.9)μm.After introducing suitable contour scanning strategy,the surface roughness of the high density and high performance sample can be mitigated to(14.4±1.1)μm,accompanied by a reduction in processing error to 0.12%.