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实验设备使用德国的Concept Laser M2激光成形机,激光波长为1064nm~1100nm,保护气体为体积分数为0.9999的氩气。成形材料使用无锡飞尔康公司生产的TC4钛合金粉末,其平均粒径为45μm,基板为TC4钛合金[22]。
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设计了两组试验方案:第1组方案中的激光功率分别为160W, 180W和200W,扫描速率分别为800mm/s, 1000mm/s和1200mm/s,具体参量见表 1。第2组方案中壁厚分别为0.2mm, 0.4mm, 0.6mm和0.8mm,扫描路径方向分别为0°, 45°和60°,具体参量见表 2。并设计了30mm×10mm×5mm的基座承接TC4钛合金薄壁件,扫描路径方向如图 1所示,即激光扫描策略也是蛇形扫描。各组试件成形示意见图 2。
Table 1. SLM forming scheme with different laser power and scanning speeds
specimen number wall thickness+height+length/mm forming process laser power P/W scanning speedv/(mm·s-1) powder layer thickness/μm scanning interval/μm scanningstrategy 1 0.6×20×20 160 800 30 105 snake scanning 2 0.6×20×20 160 1000 30 105 snake scanning 3 0.6×20×20 160 1200 30 105 snake scanning 4 0.6×20×20 180 1000 30 105 snake scanning 5 0.6×20×20 180 1200 30 105 snake scanning 6 0.6×20×20 180 800 30 105 snake scanning 7 0.6×20×20 200 1200 30 105 snake scanning 8 0.6×20×20 200 800 30 105 snake scanning 9 0.6×20×20 200 1000 30 105 snake scanning Table 2. SLM forming scheme with different wall thicknesses and scanning path directions
specimen number wall thickness+height+length/mm forming process laser power P/W scanning speedv/(mm·s-1) powder layer thickness/μm scanning interval/μm scanningstrategy 1 0.2×30×30 180 1200 30 105 0° 2 0.4×30×30 180 1200 30 105 0° 3 0.6×30×30 180 1200 30 105 0° 4 0.6×30×30 180 1200 30 105 45° 5 0.6×30×30 180 1200 30 105 60° 6 0.8×30×30 180 1200 30 105 0° 7 0.8×30×30 180 1200 30 105 45° 8 0.8×30×30 180 1200 30 105 60° -
试件成形后,采用三坐标测量仪随机测量试件上的18个点,以其平面度作为变形。为了测量距离试样表面不同深度的残余应力,采用X射线应力测定仪(X-350A型)首先测定了试样未处理表面的残余应力,然后依次采用400目、600目、800目和1200目砂纸对试样表面进行粗磨并测量其表面残余应力,最后通过电解抛光(电解溶液是高氯酸和无水醋酸体积比1:4)得到30μm和80μm深度的表面并测量其表面残余应力。试件上X射线应力测量点如图 3所示。
激光选区熔化成形TC4钛合金薄壁件变形与残余应力
Deformation and residual stress of TC4 titanium alloy thin-wall parts by selective laser melting
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摘要: 增材制造(3-D打印)作为一种近净成形技术,为钛合金薄壁件高质量毛坯制造提供了新途径,但在薄壁件成形过程中产生的变形与残余应力会影响试件的成形质量与后续加工。为了解决这一问题,采用激光选区熔化成形TC4钛合金薄壁件,研究了激光功率、扫描速率、薄壁厚度和扫描路径方向对试件变形与残余应力的影响,测量了试件不同深度的表面残余应力。结果表明,变形主要在薄壁件顶层两侧,最大残余应力主要分布在试件底层与薄壁件中间;当激光功率为180W、扫描速率为1200mm/s时,试件变形最小;当壁厚为0.6mm、扫描路径方向45°时,试件残余应力最小;薄壁件的未处理表面残余应力大于内层表面残余应力。该研究为钛合金薄壁高质量毛坯制造提供了技术帮助。Abstract: Additive manufacturing (3-D printing) is a near-net forming technology. It provides a new way for manufacturing high quality blanks of thin-wall titanium alloy parts. However, in the forming process of thin-wall parts, deformation and residual stress will affect forming quality and subsequent processing of the specimens. In order to solve this problem, TC4 titanium alloy thin-wall parts were formed by selective laser melting. The effects of laser power, scanning speed, thickness of thin-wall and direction of scanning path on deformation and residual stress of specimens were studied. Surface residual stresses at different depths were measured. The results show that deformation occurs mainly on both sides of the top layer of thin-wall parts. The maximum residual stress is mainly distributed in the bottom and the middle of thin walls. With laser power of 180W and scanning speed of 1200mm/s, the deformation of specimen is the smallest. With wall thickness of 0.6mm and scanning path direction of 45°, residual stress of the specimen is the smallest. Residual stress of the untreated surface of thin-walled parts is larger than that of the inner surface. This research provides technical assistance for the manufacture of high quality thin-wall titanium alloy blanks.
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Table 1. SLM forming scheme with different laser power and scanning speeds
specimen number wall thickness+height+length/mm forming process laser power P/W scanning speedv/(mm·s-1) powder layer thickness/μm scanning interval/μm scanningstrategy 1 0.6×20×20 160 800 30 105 snake scanning 2 0.6×20×20 160 1000 30 105 snake scanning 3 0.6×20×20 160 1200 30 105 snake scanning 4 0.6×20×20 180 1000 30 105 snake scanning 5 0.6×20×20 180 1200 30 105 snake scanning 6 0.6×20×20 180 800 30 105 snake scanning 7 0.6×20×20 200 1200 30 105 snake scanning 8 0.6×20×20 200 800 30 105 snake scanning 9 0.6×20×20 200 1000 30 105 snake scanning Table 2. SLM forming scheme with different wall thicknesses and scanning path directions
specimen number wall thickness+height+length/mm forming process laser power P/W scanning speedv/(mm·s-1) powder layer thickness/μm scanning interval/μm scanningstrategy 1 0.2×30×30 180 1200 30 105 0° 2 0.4×30×30 180 1200 30 105 0° 3 0.6×30×30 180 1200 30 105 0° 4 0.6×30×30 180 1200 30 105 45° 5 0.6×30×30 180 1200 30 105 60° 6 0.8×30×30 180 1200 30 105 0° 7 0.8×30×30 180 1200 30 105 45° 8 0.8×30×30 180 1200 30 105 60° -
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