摘要
A new severe plastic deformation method for manufacturing tubes made of AZ31 magnesium alloy with a large diameter was developed,which is called the TCESE(tube continuous extrusion−shear−expanding)process.The process combines direct extrusion with a two-step shear−expanding process.The influences of expanding ratios,extrusion temperatures on the deformation of finite element meshes,strain evolution and flow velocity of tube blanks during the TCESE process were researched based on numerical simulations by using DEFORM-3D software.Simulation results show that the maximum expanding ratio is 3.0 in the TCESE process.The deformation of finite element meshes of tube blanks is inhomogeneous in the shear−expanding zone,and the equivalent strains increase significantly during the TCESE process of the AZ31 magnesium alloy.A extrusion temperature of 380°C and expanding ratio of 2.0 were selected as the optimized process parameters from the numerical simulation results.The average grain size of tubes fabricated by the TCESE process is approximately 10μm.The TCESE process can refine grains of magnesium alloy tubes with the occurrence of dynamic recrystallization.The(0001)basal texture intensities of the magnesium alloy tube blanks decrease due to continuous plastic deformation during the TCESE process.The average hardness of the extruded tubes is approximately HV 75,which is obviously improved.
设计一种新型大塑性变形方法(管材连续挤压-剪切-扩径(TCESE)工艺)制备AZ31镁合金扩径管材。采用直接挤压与两道次剪切-扩径相结合的工艺,利用DEFORM-3D有限元软件,研究TCESE工艺中扩径比与挤压温度对坯料有限元网格变化、应变分布和流动速度的影响。模拟结果表明,在TCESE过程中,管材最大的扩径比可达3.0,坯料网格变化在剪切-扩径区是不均匀的,在扩径成形阶段等效应变显著增大。根据有限元模拟结果,选择380℃的挤压温度和2.0的扩径比为最优工艺参数,在该参数下制备的管材平均晶粒尺寸约为10μm,动态再结晶的发生为扩径挤压晶粒细化的主要原因。扩径管材(0001)基面织构强度在TCESE工艺中由于连续的塑性变形而降低。TCESE工艺制备的扩径管材的平均硬度明显增大,约为HV 75。
基金
financially supported by the National Natural Science Foundation of China (Nos.52071042,51771038)
the Chongqing Talent Plan,China (No.CQYC202003047)
Chongqing Natural Science Foundation,China (Nos.cstc2018jcyj AX0249,cstc2018jcyj AX0653)。
