TC4钛合金粉末在SLM工艺中的循环老化行为研究

Study on Aging Behavior of TC4 titanium alloy Powder recycled in Selective Laser Melting Process

摘要:

选区激光熔化(Selective Laser Melting, SLM)工艺采用特殊的专用金属粉末作为其成形原料。然而,金属粉末诸多指标易在成形及回收过程中发生改变,进而影响SLM成形件质量。本文研究了TC4钛合金粉末颗粒形貌、粒度分布、流动性以及成形试样的孔隙率、显微硬度等在循环利用过程中的变化规律,并对一系列性能改变的机理进行分析。结果表明：随循环次数增加,粉末颗粒形貌整体仍保持球形,表面光滑度提高；循环14次后观察不到卫星颗粒；粒度分布经历了集中-分散-集中的变化；多次循环利用后粉末的流动性显著提高；通过对粉末宏、微观的分析可知,上述性能变化趋势均与粉末中细小粉粒和卫星颗粒逐渐减少有关。成形试样孔隙率随循环利用次数增加先增大后减小；显微硬度不受TC4粉末循环利用次数影响。

Abstract:

Customized metal powder with a series of specific indexes is the core material to Selective Laser Melting (SLM) process, by which, the fabricated parts exhibit high precision in dimension and excellent properties in mechanics. While, multiple properties of the powder may change during the forming and recycling processes, and that could impair the products’ quality of SLM. This paper focused on the variation of TC4 powder’s properties, including particle morphology, particle size distribution (PSD) and flowability during the recycling process, and the underlying mechanism of the variation was proposed in the meantime. It was observed that the particles still kept morphology of sphere and became smoother with the increasing recycle times; few satellite particles were observed after recycling 14 times; the PSD experienced the course of concentration-dispersion-concentration; the recycled powder showed improved flowability；All the variation above inextricably linked with the percentage decreasing of tiny particles and satellite particles in the recycled powder.The porosity of the forming sample increased firstly and then decreased with the increasing recycle times ; recycle times of TC4 powder had no effect on microhardness.