7075铝合金激光熔丝增材制造热循环和温度梯度对熔池凝固组织的影响研究

doi:10.3901/JME.2024.01.096

摘要/Abstract

摘要： 7075铝合金兼具高比强度、低密度和良好耐腐蚀性等优点，在航空航天领域应用广泛。基于传统制备方法存在加工过程复杂、材料利用率低及零件表面精度低等问题，使用激光熔丝增材制造技术可在较短时间和较少成本下成型低缺陷高精度的7075铝合金零部件。本研究采用不同工艺参数制备了7075铝合金单层单道和单道多层增材试样，基于有限元方法系统分析了不同激光功率对沉积层温度场分布和微观组织的影响，以揭示热输入诱导的微观组织差异对7075铝合金沉积层硬度的影响机理。结果表明：随着激光功率从1 600 W增加到2 200 W，熔池峰值温度提高12.5%，温度梯度从62.8 ℃/mm减小至12.4 ℃/mm，沉积结构高温区域面积增大，熔宽增长20.85%，单道多层试样的峰值温度增幅大于单层单道。随着激光功率增加，沉积层上部、中部和下部的晶粒尺寸增大，晶界处第二相析出物含量减少，从底部至顶部均出现柱状晶至等轴晶转变。不同激光功率下增材试样在不同位置的显微硬度均达到90 HV以上。

关键词: 铝合金, 激光熔丝增材, 工艺参数, 微观组织, 温度场

Abstract: The 7075 aluminum alloy has found extensive application in the aerospace domain owing to its superior specific strength, low density, and remarkable resistance to corrosion. Laser wire additive manufacturing technology offers a promising solution to the challenges of intricate processing procedures, low material utilization rates, and imprecise surface finishes that characterize traditional preparation methods. This approach can facilitate the formation of 7075 aluminum alloy components with high accuracy and minimal defects in a shorter time and at a lower cost. This study involves the preparation of single-layer and single-layer multi-layer laser wire additive deposition layers of 7075 aluminum alloy using various process parameters. The temperature field distribution and microstructure of the deposited layer are analyzed systematically in this study using the finite element method, with a particular focus on how varying laser power levels affect them. Subsequently, the study elucidates the influence mechanism of the microstructure variation caused by heat input on the hardness of the 7075 aluminum alloy deposit. The results show that when the laser power is increased from 1 600 W to 2 200 W, the peak temperature of the molten pool increases by 12.5% and the temperature gradient decreases from 62.8 ℃/mm to 12.4 ℃/mm. Simultaneously, an increase in the high temperature zone area of the deposition structure is observed, along with a 20.85% rise in the melting width. The peak temperature increase of the single-channel multi-layer deposition layer is greater than that of the single-layer single-channel deposition layer. The grain size in the upper, middle, and lower parts of the deposition layer grows as the laser power is raised. Moreover, the second phase precipitate content at the grain boundary decreases, and the deposition layer experiences a columnar to equiaxed crystal transition from its bottom to the top. The microhardness of the deposited samples is greater than 90 HV at various positions and laser power levels.

Key words: aluminum alloy, laser wire additive manufacturing, process parameters, microstructure, temperature field

中图分类号:

TG156

高转妮, 王磊磊, 李响, 刘志强, 吕飞阅, 黎一帆, 占小红. 7075铝合金激光熔丝增材制造热循环和温度梯度对熔池凝固组织的影响研究[J]. 机械工程学报, 2024, 60(1): 96-118.

GAO Zhuanni, WANG Leilei, LI Xiang, LIU Zhiqiang, Lü Feiyue, LI Yifan, ZHAN Xiaohong. Effect of Thermal Cycle and Temperature Gradient on Solidification Microstructure of Deposition Layer during 7075 Aluminum Alloy Laser Wire Additive Manufacturing[J]. Journal of Mechanical Engineering, 2024, 60(1): 96-118.

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