激光功率对SLM增材制造铝合金焊缝组织及力学性能的影响

Effect of Laser Power on Microstructure and Mechanical Properties of Aluminum Alloy Welding Seam by SLM Additive Manufacturing

采用激光选区熔化成形(SLM)增材制造的铝合金(AlSi10Mg)试件进行激光焊试验,通过OM、SEM、EDS技术分析和力学性能测试,研究激光功率对SLM增材制造AlSi10Mg合金焊缝组织及力学性能的影响,结果表明,激光焊接热影响区宽度在50μm左右,宽度较窄,焊缝区为柱状枝晶组织;随着激光焊接功率的增大,激光能量增加,熔深变大,焊缝区硬度和接头抗拉强度均减小,伸长率变低,分别为4.1%、3.4%、3.1%,焊缝区一次枝晶间距和组织逐渐变大,合金中Si元素更易聚集,使得网状Al-Si共晶断裂分离,而Mg元素含量较少,变化不大;激光焊接焊缝中分布着气孔,且越往表面气孔越大,气孔减少了横截面的有效承载面积,其局部应力集中加速了裂纹的扩展,激光焊接中减少或避免气孔的产生将变得非常重要;接头断面呈现出类似河流花样的形貌,具有脆性断裂的特征。

In this paper,the aluminum alloy(AISiloMg)additive manufacturing by selective laser melting(SLM)was used for laser welding experiments,and then the effects of laser power on microstructure and mechanical properties of AiSiloMg alloy welding seam by SLM additive manufacturing were studied by OM,SEM and EDS technical analysis,and mechanical properties testing.The results show that the width of the laser-selective melting heat affected zone is small.The weld zone is columnar dendrite structure.With the increase of laser welding power,the laser energy increases,the melting depth increases,the hardness of the weld zone and the tensile strength of the joint decrease,and the elongation is low,(4.1%,3.4%,and 3.1%,respectively).The primary dendrite spacing and microstructure in the weld zone gradually increase,and Si element is easier to aggregate in the alloy,leading to the fracture separation of reticular Al-Si eutectic,while Mg element content is small,and there is little change.The pores are distributed in the welding seam of laser welding,and the pores are larger towards the surface.Because the pores reduce the effective bearing area of the cross section,and the local stress concentration accelerates the crack propagation,it is very important to reduce or avoid the pores in laser welding.Finally,the fracture section of the joint shows the appearance of a river pattern with the characteristics of brittle fracture.