(1. 華南理工大學(xué) 機(jī)械與汽車工程學(xué)院，國(guó)家金屬材料近凈成形工程技術(shù)研究中心，廣州 510640；
2. 廣州昶聯(lián)熱等靜壓材料制造有限公司，廣州 511470)
摘 要: 本文設(shè)計(jì)一種上下層致密、中間多孔的“三明治”梯度結(jié)構(gòu)材料，多孔層分別采用19.6、23.0和333.3 J/mm3的能量密度制備出A、B、C三種不同孔隙率的梯度結(jié)構(gòu)，并對(duì)其組織和力學(xué)性能進(jìn)行研究。結(jié)果表明：A型結(jié)構(gòu)孔洞是無明顯取向的連通孔，多孔層看不到明顯的初生β柱狀晶；B型結(jié)構(gòu)是大量孤立孔伴隨少量垂直于成形方向的連通孔，含有少量不連續(xù)的β柱狀晶；C型結(jié)構(gòu)多孔層的孔洞是截面為近圓形的孤立孔，多孔層中存在粗大的等軸晶。A型結(jié)構(gòu)下致密層和多孔層的結(jié)合強(qiáng)度僅為72.3 MPa，在熱應(yīng)力作用下產(chǎn)生開裂；B型結(jié)構(gòu)的拉伸強(qiáng)度可以達(dá)到979.1 MPa，伸長(zhǎng)率為4.54%；C型結(jié)構(gòu)的抗拉強(qiáng)度為1121.7 MPa，伸長(zhǎng)率為7.05%。A、B、C型梯度結(jié)構(gòu)的壓縮彈性模量分別為19.7、31.5和43.7 GPa。
關(guān)鍵字: SLM；Ti-6Al-4V；梯度結(jié)構(gòu)；組織結(jié)構(gòu)；力學(xué)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
