粉末特性对激光选区熔化过共晶Al-20Si合金微观组织和性能的影响

Effect of powder characteristic on microstructure and properties of selected laser melted hypereutectic Al-20Si alloy

过共晶Al-20Si合金因具有轻质、低的热膨胀系数、较好的耐磨性和优异的综合力学性能等在航空、航天以及电子等领域获得广泛应用。文中采用激光选区熔化技术,研究粉末特性对过共晶Al-20Si合金微观组织和性能的影响。研究发现,激光选区熔化不同粉末特性Al-20Si合金微观组织均由热影响区和基体区组成。但是混合粉末凝固时由于激光作用时间较短,纯粉末未发生完全的合金化,导致凝固后组织内部存在大量孔隙等缺陷。混合粉凝固后组织主要由粗大的不规则初晶硅颗粒和短棒状与颗粒状的共晶硅相组成。激光选区熔化后雾化粉样品存在少量的不规则初晶硅颗粒,共晶硅相主要呈现纤维状和颗粒状。XRD分析表明,与混合粉相比,雾化粉合金具有相对高的固溶度和致密度,因此导致其具有高的硬度值,且硬度值分布比较均匀。

Hypereutectic Al-20 Si alloy had been widely used in aviation,aerospace and electronics due to its light weight,low coefficient of thermal expansion,good wear resistance and excellent comprehensive mechanical properties.In this paper,the effect of powder characteristic on the microstructure and properties of hypereutectic Al-20 Si alloy was investigated by selective laser melting technique.It was found that the microstructure of Al-20 Si alloy consisted of heat affected zone and matrix zone in both the alloying powders and the mixed powders.However,when the mixed powder was solidified,the laser kept a short time and the powder was difficult to be completely melted,resulting in a large number of defects such as pores.The structure of Al-20 Si alloy mainly consisted of coarse irregular primary silicon particles and short rod-like as well as granular eutectic silicon phases for the mixed Al-20 Si powder.A small amount of irregular primary silicon particles existed in the atomized powder sample after selective laser melting,and the eutectic silicon phase presented morphologies of fibrous and granular.XRD analysis showed that the atomized powder alloy was characterized by a relatively high density and solid solubility compared with the mixed powder,which contributed to the high and a uniform distribution of hardness.