声-磁耦合调控铝/钢非均匀颗粒增强复合焊缝形成机理及微观力学响应研究

Problems of brittle intermetallic layers, residual thermal stress and weak interface bonding exist in the welding for aluminum alloy and steel, which have restricted the lightweight of engineering structures such as automobile. At present, it only depends on reducing thickness of intermetallic layers to improve the welding quality in current research, and it is not applicable for larger scope. Therefore, this project aims at the research on new method and fundamental of ultrasonic-magnetic assisted welding, and leads to weld metal composites, inhomogeneous distribution of reinforcing particles, strengthening-toughening of welded joints and releasing residual stresses. This project plans to solve the scientific problems as follows. Study the instantaneous coupling characteristics, dissolution and diffusion behavior of elements and formation and distribution of intermetallic particles, then the evolution laws of particulate reinforced weld are obtained. Study the mechanism of micro-mechanical response, distribution and changes of residual thermal stress and mechanism of interface bonding, then the structure–performance relations and strengthening-toughening mechanisms of welded joints are revealed. Optimize the ultrasonic-magnetic-coupling assisted welding process, and then the evidence for engineering practice is provided. At present, very few studies on ultrasonic-magnetic assisted welding or inhomogeneous particulate reinforced weld have been reported. This study is expected to invent a new method for welding aluminum alloy and steel, to provide a new idea for solving problems of joining dissimilar metal and to develop a new way for application energy field in the welding field. It is of academic value to enrich inhomogeneous particulate reinforced metal composites and to develop bonding theory.

铝和钢的焊接中存在脆性金属间化合物层、残余热应力较大和界面结合薄弱等问题，制约了汽车等工程结构轻量化。目前研究往往仅依赖减薄金属间化合物层以改善焊接质量，适用性受限。为此，本项目拟研究声-磁复合焊接方法及相关理论，实现焊缝结构复合化、增强颗粒分布非均匀化、接头性能强韧化，并缓解残余热应力。本项目旨在解决以下科学问题：研究多场瞬态耦合特性、元素溶解和扩散行为、金属间化合物颗粒形成和分布，进而掌握复合焊缝结构演变规律；研究微观力学响应机制、残余热应力分布和变化、界面结合机理，进而阐明焊缝结构与力学性能的关系，揭示接头强韧化机理；优化复合焊接工艺，进而为工程实践提供依据。目前鲜有声-磁复合焊接和非均匀颗粒增强复合焊缝结构的研究。本研究有望为铝和钢高强焊接提供新思路，为解决异种金属连接关键问题探索新方法，为能场在焊接领域的应用拓展新路径，对丰富非均匀颗粒增强复合结构和发展连接理论具有学术价值。

研究了声场作用下，固相金属表面塑性变形、氧化膜破裂等行为，分析元素扩散、物相迁移、非平衡凝固等规律，结合多维、多尺度数值模拟结果，揭示接头组织形成机理，实现接头可控连接；研究焊缝合金、第二相/焊缝合金界面、母材/焊缝合金界面等接头组织的结构和热传输特性，明确固溶体、非晶层、反应物等结构对高导热、强结合的影响，建立描述接头组织热导性的模型，分析导热性能，揭示接头高热导产生机制。建立声（热）学参量-接头组织-热（力）学性能的响应关系，降低接头热阻，分析缺陷的产生和防止方法，实现可靠连接。..