Integrated physical and numerical simulations of weld seam formation during extrusion of magnesium alloy
Integrated physical and numerical simulations of weld seam formation during extrusion of magnesium alloy
复制标题
镁合金挤压过程中焊缝形成的综合物理和数值模拟
DOI：
10.1016/j.jmatprotec.2018.10.025
复制
发表时间：
2019-04-01
影响因子：
6.3
通讯作者：
Zhou, Jie
中科院分区：
文献类型：
--
作者：
Bai, Sheng-wen;Fang, Gang;Zhou, Jie
固态键合发生在挤压过程中，通过舷窗模具生产空心金属型材，称为挤压焊接。焊缝缺陷会降低挤压产品的机械性能。采用物理与数值模拟相结合的方法，研究挤压条件对Mg-8Al-0.5Zn-0.5RE镁合金纵向焊缝质量的影响。设计了一种用于物理模拟的专用模组，通过该模组将两根镁合金棒在高静水压力下进行固态焊接。进行了不同条件下的挤压焊接试验。结果表明，采用这种模具设置，可以物理模拟挤出过程中焊缝的形成，以生产空心型材。然后对挤压焊接实验进行数值模拟，揭示了无法通过实验测量的应变、应力和静水压力。最后，测定了挤压焊接镁合金的抗拉强度和伸长率，并对其组织进行了分析。结果表明：随着挤压速度的降低和挤压温度的升高，结合强度增大；对于粘合良好的棒材，在光学显微镜下看不到焊缝。高温和大等效应变导致界面发生完全的动态再结晶，导致平均晶粒尺寸减小，焊缝消失。采用物理与数值模拟相结合的方法，对特定镁合金的挤压工艺参数进行优化，以保证挤压中空型材的焊缝质量。
Solid-state bonding takes place during the extrusion process to produce a hollow metal profile through a porthole die, known as extrusion welding. Defective weld seams degrade extruded products in mechanical properties. The present research was aimed to determine the effect of extrusion condition on the longitudinal weld seam quality of a magnesium alloy, Mg-8Al-0.5Zn-0.5RE, using an integrated physical and numerical simulation method. A special die set-up for physical simulation was designed, through which two magnesium alloy rods were welded in the solid-state under high hydrostatic pressure. Extrusion welding experiments under different conditions were performed. It was demonstrated that, with this die set-up, the formation of weld seams during extrusion to produce hollow profiles could be physically simulated. The extrusion welding experiments were then numerically simulated to reveal strains, stresses and hydrostatic pressures that could not be experimentally measured. Finally, the tensile strength and elongation of the extrusion-welded magnesium alloy were determined and its microstructure was examined. The results showed that the bonding strength increased with decreasing extrusion speed and rising extrusion temperature. For well-bonded rods, weld seam was invisible under optical microscope. Attributed to high temperature and large equivalent strain, complete dynamic re crystallization occurred across the interface, leading to a reduced average grain size and disappearance of weld seam. By applying the integrated physical and numerical simulation method, extrusion process parameters for a particular magnesium alloy can be optimized to ensure weld seam quality of extruded hollow profiles.