激光选区熔化成形含锆7×××系铝合金的显微组织与力学性能  

Microstructures and mechanical properties of zirconium-containing 7×××aluminum alloy prepared by selective laser melting

作　　者：詹强坤 刘允中[1] 刘小辉[1] 周志光 ZHAN Qiang-kun;LIU Yun-zhong;LIU Xiao-hui;ZHOU Zhi-guang(National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials,South China University of Technology,Guangzhou 510641,China)

机构地区：[1]华南理工大学国家金属材料近净成形工程技术研究中心,广州510641

出　　处：《材料工程》2021年第6期85-93,共9页Journal of Materials Engineering

基　　金：广东省重点领域研发计划项目(2019B090907001);广东省科技计划项目(2014B010129002)。

摘　　要：热裂问题是激光选区熔化成形(SLM)7×××系铝合金面临的主要障碍之一。通过低能球磨工艺制备ZrH_(2)/7075复合粉末,采用激光选区熔化技术制备含锆7×××系铝合金材料,分析了不同ZrH_(2)添加量(0.5%,1.0%,1.5%,质量分数,下同)对试样显微组织和力学性能的影响规律。结果表明:随着ZrH_(2)含量的增加,SLM试样的柱状晶组织逐渐消失,热裂纹逐渐减少,当ZrH_(2)含量为1.5%时,试样显微组织完全转变为细小等轴晶(平均晶粒尺寸为1.6μm),热裂纹完全消除。ZrH_(2)在SLM成形过程中与铝熔体原位反应形成L1_(2)型Al_(3)Zr相,L1_(2)型Al_(3)Zr相的异质形核作用促进了柱状晶到等轴晶的转变,抑制了热裂纹的产生。经T6热处理后,试样抗拉强度为(550±10)MPa,屈服强度为(490±5)MPa,伸长率为(12±1)%,断口处存在大量韧窝,表现为韧性断裂。The preparation of 7×××series aluminum alloy by selective laser melting technology(SLM)is hindered by hot tearing.Novel ZrH_(2)modified 7075 composite powders were prepared by the low-energy ball milling technology.Zirconium-containing 7×××series aluminum alloy was then prepared by the SLM process.The microstructure and mechanical properties of the samples with different ZrH_(2)contents(0.5%,1.0%,1.5%,mass fraction,the same below)were systematically investigated.The results show that the addition of ZrH_(2)can significantly reduce hot tearing and change the microstructure.When 1.5%ZrH_(2)is added,the hot tearing is completely eliminated and the grain microstructure is entirely composed of fine equiaxed grains.The transition of columnar grains to equiaxed grains is attributed to the in-situ formation of L1_(2)-Al_(3)Zr which provides numerous nucleation positions for solidification.After T6 heat treatment,the tensile strength,yield strength and elongation of SLMed sample are(550±10),(490±5)MPa and(12±1)%,respectively.Fractography analysis shows a large number of dimples on the fracture surface after tensile testing,indicating ductile fracture mode.

关 键 词：7×××系铝合金 ZrH_(2) 激光选区熔化 热裂纹 力学性能 

分 类 号：TG146.21[一般工业技术—材料科学与工程]