选择性激光熔化技术(Selective Laser Melting, SLM) 是最近十几年发展起来的一种先进快速成形技术, 利用高能激光束熔化金属粉末, 逐层堆积, 直接成形高性能复杂金属零部件。SLM可成形的粉末材料广泛, 其中铝合金作为轻金属材料有优良的物理、化学和机械性能, 在很多领域获得了广泛应用, 但是铝合金自身的特性(如易氧化, 高反射性和导热性等)增加了选择性激光熔化制造的难度。研究使用AlSi12铝合金粉末对SLM成形工艺优化做了一系列试验研究, 利用金相显微(OM)、电镜扫描(SEM)等方法分析了扫描轨迹和成形件的组织性能。采用不同工艺参数组合, 在铝合金基板上进行铝合金粉末单道熔化实验, 研究了激光功率、扫描速度对单熔化道形貌和宽度的影响规律; 最终单道实验得出的优化工艺窗口, 要求线能量密度在0.17～0.36 J/mm范围内。在优化的工艺窗口内, 实施单层多道扫描, 分析扫描间距和搭接率对单层形貌的影响规律, 并进一步优化激光功率和扫描速度参数, 得到较优工艺参数是激光功率140～180 W, 扫描速度700～1 000 mm/s, 扫描间距0.04～0.05 mm。最后, 实施块体成形, 分析了成形件致密度与线能量密度的关系, 并对成形件的性能作了微观表征, 从粉末特性和工艺参数两方面分析孔隙的成因。

Selective laser melting(SLM)has been developed as a new advanced rapid prototyping technology. Metal parts with advanced properties and complexity are directly manufactured with the SLM technology. Aluminum alloy is a light metal with excellent strength-to-weight ratio. However, some of its inherent properties, i.e. ease of oxidization, high reflectivity and thermal conductivity, make it difficult for aluminum alloy parts to be manufactured by SLM. In this study, a series of experiments have been conducted to optimize the processing parameters of SLM-built parts using AlSi12 power. Scan tracks as well as the structure and properties of built parts were analyzed with the optical microscope(OM), Scanning Electron Microscope(SEM)etc. Single track scanning experiments were conducted on a substrate With a thin layer of AlSi12 powder under different processing parameters (the laser power P and the scan speed V). Optimum parameters for single track scanning were obtained so that the linear energy density should be in the range of 0.17～0.36 J/mm. Multi-track experiments were then performed to find the relations between scanning spacing, overlapping ratio and the surface morphology. A processing window was obtained as 140～180 W for laser power, 700～1 000 mm/s for scanning speed and 0.04～0.06 mm for hatch spacing. Blocks are fabricated to reveal the relation between the linear energy density and the resulting part density. The reason of porosity and balling effects are discussed from the perspective of powder properties and process parameters.