摘要
激光熔覆是新兴的表面强化技术,具有工艺精度高、可控性好、组织细密、热畸变小等特点,在汽车、能源、电子、航空航天等领域得到广泛应用。激光熔覆过程中出现的微裂纹、气孔等微观缺陷严重影响了该技术的推广。超声振动的高频低幅振动可影响熔覆层凝固微观组织,有效减少微观缺陷。本研究基于相场法建立了超声振动下碟片激光器激光熔覆熔池凝固过程的动态模型,通过编程对模型进行求解,揭示了不同振幅下的多晶凝固组织,同时对熔覆凝固行为进行了实验微观表征,二者结论相吻合。研究表明,超声振动可有效细化熔覆层组织结构,促进结晶凝固形核,改变枝晶择优取向。振动不影响主枝晶臂的生长速度,对主枝晶臂宽度、二次枝晶臂的形成、生长速度和竞争生长影响明显。随着超声振幅增大,枝晶臂趋于茂盛,竞争生长明显,间接减少了凝固组织中气孔、裂纹形成,过大的超声振幅不会进一步改变枝晶形貌。该研究为超声振动下激光熔覆实践应用提供理论指导,为精确控制凝固组织提供重要的理论依据。
Laser cladding is an emerging surface strengthening technology,which has the characteristics of high process accuracy,good controllability,fine structure,and small thermal distortion.It is widely used in the fields of automobiles,energy,electronics,aerospace and other fields.The micro-cracks,pores and other micro-defects that appeared in the laser cladding process seriously affected the promotion of this technology.Ultrasonic vibration uses high-frequency and low-amplitude vibration,which can affect the cladding and solidification microstructure and effectively reduce microscopic defects.Based on the phase field method,a dynamic model of the laser cladding bath solidification process of a disc laser under ultrasonic vibration was established,and the model was solved by programming,revealing the polycrystalline solidification structure under different amplitudes,and at the same time,the cladding solidification behavior was experimentally characterized.The two conclusions are in good agreement.Studies have shown that ultrasonic vibration can effectively refine the structure of the cladding layer,promote crystal solidification and nucleation,and change the preferred orientation of dendrites.Vibration does not affect the growth rate of the main dendrite arm,but has obvious effects on the width of the main dendrite arm,the formation of the secondary dendrite arm,the growth rate and the competitive growth.With the increase of ultrasonic amplitude,the secondary and tertiary dendrite arms tend to flourish,and the competitive growth is obvious,which indirectly reduces the formation of pores and cracks in the solidified structure.Excessive ultrasonic amplitude will not further change the dendrite morphology.This research provides theoretical guidance for the practical application of laser cladding under ultrasonic vibration,and provides an important theoretical basis for precise control of the solidification structure.
作者
高敬翔
李昌
陈正威
韩兴
GAO Jingxiang;LI Chang;CHEN Zhengwei;HAN Xing(School of Mechanical Engineering and Automation,University of Science and Technology Liaoning,Anshan 114051,China)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2021年第12期12161-12168,共8页
Materials Reports
基金
国家自然科学基金(E050402/51374127)
公安部武警消防重点实验室开放课题(KF201704)
辽宁省自然科学基金指导计划项目(2019ZD0277)
辽宁科技大学创新团队建设项目(601009830)。
关键词
超声振动
激光熔覆
相场法
碟片激光器
凝固机理
ultrasonic vibration
laser cladding
phase field method
disk laser
solidification mechanism
