摘要
针对激光熔化沉积冶金组织与缺陷,借鉴激光摆动焊接技术,提出一种激光摆动送粉增材制造TC4钛合金工艺,借助激光原位摆动改变熔池运动轨迹进而影响温度梯度和凝固速率,改善增材制造钛合金的微观组织。利用OM、SEM、EBSD和Vickers硬度计研究了激光摆动送粉增材制造工艺对TC4钛合金微观组织演变及力学性能的影响。结果表明,无摆动激光熔化沉积实验的最佳工艺参数为:激光功率1000 W,扫描速率8 mm/s,送粉速率6.92 g/min;直线型激光摆动的最佳工艺参数为:摆动频率200 Hz,摆动幅度1.5 mm。直线型激光摆动对熔池形貌改善显著,气孔和裂纹等缺陷较少,柱状晶数量和尺寸均有所减小,并且晶粒出现了等轴化的现象。相比无摆动样品,激光摆动后Ti-6Al-4V合金单道区域平均晶粒尺寸从5.20μm减小到4.37μm;硬度从418.00 HV提升到428.75 HV。
Laser melting deposition(LMD) combines the laser cladding and rapid prototyping manufacturing technologies, and can be used for swift prototyping of complex parts with excellent comprehensive properties. However, due to its unique metallurgical conditions, it is easy to develop penetrating columnar crystals and coarse primary grains along the building direction. This remarkably reduces the mechanical properties of the alloy. The root cause of this issue can be traced back to the thermodynamic and dynamic metallurgical processes. Thus, this study proposes an oscillating laser melting deposition(OLMD) based on laser oscillating welding technology, and aims to elucidate the metallurgical structure and defects of laser melt deposition. OLMD modifies the motion trajectory of the molten pool using a laser in situ oscillation, and directly impacts the temperature gradient and solidification rate, thus improving the microstructure of titanium alloy by LMD. Furthermore, the microstructure evolution and mechanical properties of TC4 titanium alloy produced using OLMD were studied using OM, SEM, EBSD, and a Vickers hardness tester. The results indicate that the optimum process parameters of laser melting deposition without oscillation are as follows: the laser power is 1000 W, scanning rate is 8 mm/s, and powder feeding rate is 6.92 g/min. The optimum technological parameters of linear oscillation are as follows: the frequency is 200 Hz and the oscillation amplitude is 1.5 mm. Addition of linear laser oscillation considerably improved the morphology of the molten pool, and defects such as porosity and cracks were not observed. The overall number and size of columnar crystals reduced, and the grains were equiaxed. When compared to the sample without oscillation, the average grain size of Ti-6Al-4V alloy with linear oscillation decreased from 5.20 μm to 4.37 μm, while hardness increased from 418.00 HV to 428.75 HV.
作者
方远志
戴国庆
郭艳华
孙中刚
刘红兵
袁秦峰
FANG Yuanzhi;DAI Guoqing;GUO Yanhua;SUN Zhonggang;LIU Hongbing;YUAN Qinfeng(Tech Institute for Advanced Materials,College of Materials Science and Engineering.Nanjing Tech University,Nanjing 210009,China;School ofMaterials Engineering,Shanghai University ofEngineering Science,Shanghai 201620,China;Zhejiang Shenji Titanium Indusiry Co.,Ltd,Huzhou 313306,China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2023年第1期136-146,共11页
Acta Metallurgica Sinica
基金
国家自然科学基金项目No.51875274
浙江省重点研发计划项目No.2021C01085
江苏高校优势学科建设工程项目
关键词
增材制造
激光熔化沉积
激光摆动
组织演变
additive manufacturing
laser melting deposition
laser oscillation
microstructure evolu-tion
