铺粉厚度对选区激光熔化GH3625组织与力学性能的影响

Influence of layer thickness on the microstructure and mechanical properties of selective laser melting processed GH3625

在不同铺粉厚度下使用相同的激光工艺参数制备GH3625合金,并对选区激光熔化GH3625的组织与力学性能的进行了分析.结果表明,在较大的工艺窗口内,铺粉厚度由0.02mm增加至0.03mm不会影响打印质量,并且在优化的工艺参数窗口下均能制备得到致密度99.9%以上的块体.铺粉厚度的增加会导致熔池形态发生改变,也会明显改变晶粒形态.当铺粉厚度为0.02mm时,晶粒多为细长形,平均晶粒尺寸约为18.128μm,晶粒有明显的择优取向.此时,相邻的熔池形态差别较大,呈现一道次较深较宽,另一道次较浅较窄的现象.而铺粉厚度增加至0.03mm后温度梯度差异减少,相邻熔池形态差别较小,组织中细长形晶粒减少,平均晶粒尺寸降低至11.921μm,晶粒的择优取向也相应减弱.由于晶粒形态的改变,在垂直方向上,铺粉厚度为0.03 mm的样品的屈服强度相比于铺粉厚度为0.02mm的屈服强度提高了5%,有效抑制了打印态样品的各向异性程度.创新点:(1)在优化的工艺窗口内,工艺参数不变,铺粉厚度的改变同样能够制备出成形良好且致密的样品.(2)增加铺粉厚度减弱了晶粒的择优取向,并相应的减少打印态样品力学性能的各向异性程度.

To investigate the influence of layer thickness on the microstructure and mechanical properties of laser powder bed fusion processed GH3625,specimens were prepared with different layer thickness while other parameters remained unchanged before they were studied in aspect of microstructure and tensile properties.It is shown that the density of specimens has not been influenced by layer thickness under a wide range of processing parameters.Besides,with optimized processing parameters,specimens with a density over 99.9%can be fabricated by 0.02 mm and 0.03 mm layer thickness at the same time.The increase of the layer thickness will lead to the change of molten pool morphology,and also significantly change the grain morphology.When the thickness of powder bed was 0.02 mm,the average grain size was about 18.128μm,and the grain had obvious preferential orientation.At this time,the adjacent molten pools differ greatly in shape,showed the phenomenon that one secondary was deeper and wider,and the other secondary was shallow and narrow.When the layer thickness increased to 0.03 mm,the temperature gradient difference decreased,the morphology difference of adjacent molten pools was small,the elongated grains in the microstructure decreased,the average grain size decreased to 11.921μm,and the preferred orientation of grains also weakened.Due to changes in grain structure and grain size,the yield strength was increased by about 5%in the 0.03 mm specimen than that of the 0.02 mm specimen in vertical direction,contributing to less anisotropy in mechanical property.Highlights:(1)Under an optimized process,although with the same pramaters,high density specimens can still be obtained with larger layer thickness.(2)The increase in layer thickness weakens the texture in the microstructure and therefore restrains the anisotropic features.