选区激光熔化成形工艺对多孔TC4钛合金显微组织的影响

Influence of Selective Laser Melting Forming Process on Microstructure of Porous TC4 Titanium Alloy

采用Rhino软件构建了泰森多边形不规则多孔结构,利用选区激光熔化(SLM)技术成形多孔TC4钛合金,研究了激光功率(180,200,220 W)、扫描速度(1200,1600,2000 mm·s^(-1))、扫描间距(80,100,120μm)对其显微组织的影响。结果表明:随着激光功率的增大、扫描速度的减小或扫描间距的增大,SLM成形多孔TC4钛合金实体部分的微观孔洞缺陷数量和尺寸减小,相对密度提高,扫描速度是影响缺陷生成的主要原因;在激光功率220 W、扫描速度1200 mm·s^(-1)、扫描间距120μm条件下钛合金具有最少的微观孔洞缺陷,其相对密度可达99.2%。靠近多孔结构孔隙部分的截面存在等轴晶和平行于基板表面的柱状晶,而远离孔隙部分的组织主要由β柱状晶组成,柱状晶内部为与其长轴成±45°且平行排列的初生针状马氏体;随着激光功率的减小、扫描速度的增大或扫描间距的减小,柱状晶的宽度和初生马氏体的长度均减小,扫描间距对显微组织的影响更大。

An irregular porous structure of Voronoi polygon was constructed by Rhino software,and the porous TC4 titanium alloy was prepared by selective laser melting(SLM).The effects of laser power(180,200,220 W),scanning speed(1200,1600,2000 mm·s^(-1))and scanning spacing(80,100,120μm)on the alloy microstructure were investigated.The results show that with the increase of laser power,the decrease of scanning speed or the increase of scanning spacing,the number and size of micropore defects in solid part of SLM formed porous TC4 titanium alloy decreased,and the relative density increased;the scanning speed was the main reason affecting the formation of defects.Under laser power of 220 W,scanning speed of 1200 mm·s^(-1) and scanning spacing of 120μm,the titanium alloy had the fewest micropore defects with relative density of 99.2%.There were equiaxed crystals and columnar crystals parallel to the substrate plate surface in the section near the pores of the porous structure,while the microstructure far away from the pores was mainly composed ofβcolumnar crystals,and inside the columnar crystals there was primary acicular martensite arranged in parallel at±45°to its major axis.With the decrease of laser power,the increase of scanning speed or the decrease of scanning spacing,the width ofβcolumnar crystal and the length of primary martensite decreased;the scanning spacing had a greater effect on the microstructure.