异种金属激光焊接熔池动态特性及其力学行为

With the advantages of high power, high precision,high speed, high efficiency, and low deformation, laser welding has been used in joining of dissimilar metals, and played an important role in the fields of aeronautics, automobile, and electronics. Laser welding of dissimilar metals is a dynamic process with multi-field, multi-scale and multi-parameter and involves different physical phenomena. The difference in thermal-physical properites may result in residue stress and deformation, and intermetallic, which is harmful to the final propeties and quality of weldment.In the process, the core issue is the dynamic characteristic of molten pool in laser welding,which determines the final microstructure and resultant mechanical properties.By probing deeply the mechnism of heat and mass transfer, a comprehensive model is develped, incorporating the mass, momentum and energy conservation and solute transport equation, and evolution of liquid-gas interface. The objective of this project is to investigate the effects of heat and mass transfer, and fluid flow on mechanical behavior, optimize processing parameters, improve the mechanical properties, manufacturing efficiency and product quality, and to speed up the successful application of laser welding of dissimilar metal.

由于具有高功率密度、高精度、高速度、高效率和低变形等突出优点，激光焊接已经越来越广泛的应用在异种金属的焊接上，在航空航天、汽车、电子等领域中发挥着重要作用。然而，异种金属的激光焊接是一个多场、多尺度、多参数的动态复杂过程，涉及到众多物理现象。金属热物性参数的差异易使接头产生残余应力和变形，以及脆性金属间化合物，影响异种金属的激光焊接的性能和质量。其中，焊接熔池的动态特性是异种金属激光焊接中的核心问题，决定着焊件凝固后最终的力学性能。本课题从制造工艺力学的角度，通过深入研究焊接过程中的传热传质机理, 开展温度场、流体速度场、浓度场以及气-液界面演化等动态过程的耦合模拟分析，探索传热传质和熔池流体流动对力学行为的影响机制，从而进行工艺参数的定量分析与优化，获得所需要的组织和力学性能，提高异种金属激光焊接的效率和质量，满足异种金属激光焊接在不同领域的特定需求，进一步推动其在工业各领域的成功应用。

本项目主要对异种金属激光焊接热量传递、熔池形态、物质传输及力学特性进行了深入系统的研究。通过考虑异种金属激光焊接过程中的主要物理现象，建立了高密度激光异种金属焊接过程热量传递、物质传输与气液界面演化耦合的数值模型。研究了焊接过程Marangoni效应对流体流动的驱动机制，模拟分析了高密度激光异种金属焊接过程中的瞬态温度场、流场、浓度场、匙孔形态及演化过程，对焊接过程中的蒸发和溅射机制进行了系统的研究，计算分析了由此引起的能量损失及质量损失。在此基础上，针对不同材料体系，对异种金属激光焊接过程的焊接方法、工艺优化、显微组织及力学性能进行了系统深入的研究。建立了输入参数-熔池动态特性-微观组织-力学行为的对应关系。对零部件的异种金属激光焊接在工程上的具体应用进行了探索，包括发动机涡轮增压器涡轮与转轴的激光焊接、陀螺马达主体与马达盖的激光焊接、平衡支架与配重铅块的焊接等。