Al-Mg-Sc粉末激光增材修复6061-T6铝合金组织及其性能研究

Microstructure and mechanical properties of 6061-T6 alloys repaired by laser additive with Al-Mg-Sc powder

采用激光增材修复技术对预制槽的6061-T6铝合金进行修复实验,利用光学显微镜、能谱分析仪和扫描电子显微镜等观察Al-Mg-Sc激光增材修复6061-T6铝合金不同区域的微观组织,利用室温拉伸机和显微硬度计对不同热处理前后试样的力学性能进行研究。研究结果表明:修复部位无裂纹、界面熔合不良等严重缺陷,存在少量的气孔,孔隙率为0.21%。修复区中晶粒均为等轴晶,且晶粒内存在较多的Al3(Sc,Zr)粒子,起到细化晶粒的作用。部分熔化区由于靠近基体,温度梯度较大,晶粒形态为垂直界面生长的外延柱状晶。热影响区中原本细小的β’’强化相在修复过程中受到激光热循环作用后生长为粗大的β(Mg2Si)平衡相,发生过时效“软化”现象,导致其强度和硬度急剧下降,维氏硬度最低为58。修复试样的抗拉强度为200 MPa,伸长率为8.0%,分别为基体的68.97%和49.38%;进行人工时效处理后二者变化不大。当修复试样经过固溶和人工时效处理后,其各项力学性能均有所提高,其中抗拉强度286 MPa,伸长率为11.8%,分别为基体的98.62%和72.84%。

The laser additive repair technology was used to conduct repair experiments on prefabricated slotted 6061-T6 aluminum alloy.The microstructure of different areas of Al-Mg-Sc laser additive repaired 6061-T6 aluminum alloy was observed by means of optical microscope,energy dispersive spectroscopy and scanning electron microscope.The mechanical properties of the specimens before and after different heat treatments were studied by using room temperature tensile machine and micro hardness tester.The results show that there are no serious defects such as cracks and poor interfacial fusion in the repaired zone(RZ),and a small amount of pore exists with a porosity of 0.21%.The grains in the RZ are all equiaxed,and there are more Al3(Sc,Zr)particles in the grains,which play the role of refining the grains.Partial melting zone(PMZ)has a large temperature gradient near the substrate,and the grain morphology is an epitaxial columnar crystal with vertical interface growth.The original fineβ''strengthening phase in the heat-affected zone(HAZ)grows up into a coarseβ(Mg2Si)equilibrium phase after the laser thermal cycling during the repair process.The over-aging"softening"phenomenon occurs,resulting in a sharp decrease in strength and hardness,with a minimum Vickers hardness of 58.The tensile strength and elongation rate of the repaired specimens are 200 MPa and 8.0%,respectively,which are 68.97%and 49.38%of those of the matrix,and they have little change after artificial aging treatment.After solid solution and artificial aging treatment,all mechanical properties of the repaired specimens have been improved,including the tensile strength of 286 MPa and elongation rate of 11.8%,which are 98.62%and 72.84%of those of the matrix,respectively.