(1. 华南理工大学 机械与汽车工程学院，国家金属材料近净成形工程技术研究中心，广州 510640；
2. 广州昶联热等静压材料制造有限公司，广州 511470)
摘 要: 本文设计一种上下层致密、中间多孔的“三明治”梯度结构材料，多孔层分别采用19.6、23.0和333.3 J/mm3的能量密度制备出A、B、C三种不同孔隙率的梯度结构，并对其组织和力学性能进行研究。结果表明：A型结构孔洞是无明显取向的连通孔，多孔层看不到明显的初生β柱状晶；B型结构是大量孤立孔伴随少量垂直于成形方向的连通孔，含有少量不连续的β柱状晶；C型结构多孔层的孔洞是截面为近圆形的孤立孔，多孔层中存在粗大的等轴晶。A型结构下致密层和多孔层的结合强度仅为72.3 MPa，在热应力作用下产生开裂；B型结构的拉伸强度可以达到979.1 MPa，伸长率为4.54%；C型结构的抗拉强度为1121.7 MPa，伸长率为7.05%。A、B、C型梯度结构的压缩弹性模量分别为19.7、31.5和43.7 GPa。
关键字: SLM；Ti-6Al-4V；梯度结构；组织结构；力学性能
（1. National Engineering Research Center of Near-Net-Shape Forming for Metallic Material, School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China;
2. Guangzhou Zoltrix HIP Material Limited, Guangzhou 511470, China）
Abstract:A sandwich model of gradient structure was designed in this paper. The upper and lower dense layers were formed using optimal processing parameters. Three kinds of structure A, B, C with different porosity of middle layer were produced at different laser energy density of 19.6, 23.0 and 333.3 J/mm3. The microstructures and mechanical properties of gradient structures were investigated. The results show that the pore in structure A is interconnecting pores without obvious orientation. Many small isolated pores and a small amount of interconnecting pores exist in structure B. All pores in structure C with nearly circular cross-section are isolated holes. As a result, structure A has unobvious columnar grains due to the high porosity, while structure B contains some discontinuous prior β columnar grains. Structure C is consisted of coarsened equiaxed grains rather than columnar grains. The shear strength between lower dense layer and porous layer of samples with structure A is only 72.3 MPa. And it appears cracking in the forming process. Tensile strength of samples with structure B still reaches 979.1 MPa combined with elongation of 4.54%. Tensile strength of samples with structure C is 1121.7 MPa, and the elongation is as high as 7.05%. The modulus of structure A, B and C are 19.7, 31.5 and 43.7 GPa, respectively.
Key words: selective laser melting; Ti-6Al-4V; gradient structure; microstructures; mechanical properties
