(1. 重庆理工大学 材料科学与工程学院，重庆 400054；
2. 重庆大学 材料科学与工程学院，重庆 400044)
摘 要: 为了研究渐进扩径成形(Progressive expanding forming, PEF)工艺对Al/Mg双金属复合方形管材成形过程多物理场及微观组织的影响，根据PEF工艺的特点，采用DEFORM-3D软件建立了三维热力耦合的有限元数值模型并进行模拟，在PEF工艺实验中开展了微观组织表征及硬度测试，研究了预热温度对成形载荷及坯料形变的影响、挤压速度对坯料温度场及等效应力的影响，以及不同坯料预热温度对Al/Mg双金属微观组织的影响。结果表明：PEF工艺可以产生大塑性变形(Severe plastic deformation)，有效地细化双层方管的微观组织，并且能够直接一次形成壁厚为3 mm的Al/Mg双金属复合方管；坯料预热温度从340 ℃上升到430 ℃时，成形载荷呈下降趋势，下降了约28.6%；挤压速度越快，挤压剪切扩径区的等效应力越大；在Al/Mg双金属复合界面过渡区会形成Mg17Al12、MgAl、Mg2Al3三种铝镁的化合产物，结合层硬度较高；当挤压速度为10 mm/s、挤压温度为400 ℃、扩径角为150°时，方形管材Al/Mg结合层的缺陷较小，结合层的冶金结合效果理想，硬度约为138.14 HV。
关键字: 双金属；方形管材；数值模拟；渐进扩径成形；微观组织
（1. School of Materials Science and Engineering, Chongqing University of Technology, Chongqing 400054, China;
2. School of Materials Science and Engineering, Chongqing University, Chongqing 400044, China）
Abstract:In order to study the influence of progressive expanding forming (PEF) process on the multi physical field and microstructure of Al/Mg bimetallic composite square tube in the forming process, a three-dimensional thermal mechanical coupling finite element numerical model was created using DEFORM-3D, and the simulation based on the features of the PEF process was carried out. The microstructure characterization and hardness test during PEF process experiment were performed. The effects of billet preheating temperature on forming load and blank deformation, the effects of extrusion speed on billet temperature field and effective stress, the effects of different billet preheating temperatures on Al/Mg bimetallic microstructure, and the bonding layer hardness distribution were investigated. The results reveal that the PEF process can cause severe plastic deformation(SPD), efficiently improve the microstructure of a double-layer square tube, and make an Al/Mg bimetallic composite square tube with a wall thickness of 3mm in a single step. When the preheating temperature of the billet rises from 340 ℃ to 430 ℃, the forming load decreases by 28.6%. The effective stress in the extrusion shear expanding zone increases as the extrusion speed increases. Three aluminum magnesium products of Mg17Al12, MgAl and Mg2Al3 will be generated in the transition zone of the Al/Mg bimetallic composite interface, and the bonding layer will have a high hardness. When the extrusion speed is 10 mm/s, the extrusion temperature is 400 ℃ and the expansion angle is 150°, the flaws of the Al/Mg bonding layer of square tube are minor, the metallurgical bonding effect of the bonding layer is excellent, and the hardness is around 138.14 HV.
Key words: bimetallic; composite square tube; numerical simulation; progressive expanding forming; microstructure
