AZ31 Mg alloy with heterogeneous bimodal grain structure (smaller grain size of 5–20 µm and coarser grain size of 100–200 µm) was subjected to accumulated extrusion bonding (AEB) at 250 ℃ combined with two-stage artificial cooling in this work, viz. local water cooling and artificial cooling. The microstructure developed consecutively as a result of discontinuous dynamic recrystallization (DDRX) for the AEBed samples. {10–12} tensile twinning also played an important role for the AEB with local water cooling at the initial extrusion stage in the container. Local water cooling could further reduce the DRXed grain size to ∼2.1 µm comparing that without water cooling. And the grain growth rate was reduced by artificial cooling out of extrusion die. Under the combination of two-stage cooling, the fine DRXed grains at sizing band were almost retained with average grain size of ∼2.3 µm after the sheet out of extrusion die, and the unDRXed grains with high residual dislocation density accumulation were also reserved. The tensile tests results indicated that a good strength-ductility balance with a high ultimate tensile strength (319 MPa vs. 412 MPa) and fracture elongation (19.9% vs. 30.3%) were obtained. The strength enhancement was mainly owing to the grain refinement and local residual plastic strain reserved by the artificial cooling. The excellent ductility originated from fine DRXed microstructure and ED-tilt double peak texture.

本文对具有异质双峰晶粒结构（较小晶粒尺寸为 5-20 µm，较粗晶粒尺寸为 100-200 µm）的 AZ31 镁合金在 250 ℃ 下进行累积挤压结合（AEB）并结合两级人工冷却，即。局部水冷却和人工冷却。由于 AEBed 样品的不连续动态再结晶 (DDRX)，微观结构不断发展。{10–12}拉伸孪生对于在容器中初始挤出阶段采用局部水冷却的 AEB 也发挥了重要作用。与没有水冷却的情况相比，局部水冷却可以进一步将 DRX 晶粒尺寸减小至 ∼2.1 µm。并通过挤压模外人工冷却降低了晶粒长大速率。在两级冷却的结合下，板料脱离挤压模后，定径带处细小的 DRX 晶粒几乎被保留，平均晶粒尺寸约为 2.3 µm，并且还保留了具有高残余位错密度积累的未 DRX 晶粒。拉伸试验结果表明，获得了良好的强度-延展性平衡，具有较高的极限拉伸强度（319 MPa vs. 412 MPa）和断裂伸长率（19.9% vs. 30.3%）。强度的提高主要是由于人工冷却所保留的晶粒细化和局部残余塑性应变。优异的延展性源自精细的 DRX 微观结构和 ED 倾斜双峰织构。拉伸试验结果表明，获得了良好的强度-延展性平衡，具有较高的极限拉伸强度（319 MPa vs. 412 MPa）和断裂伸长率（19.9% vs. 30.3%）。强度的提高主要是由于人工冷却所保留的晶粒细化和局部残余塑性应变。优异的延展性源自精细的 DRX 微观结构和 ED 倾斜双峰织构。拉伸试验结果表明，获得了良好的强度-延展性平衡，具有较高的极限拉伸强度（319 MPa vs. 412 MPa）和断裂伸长率（19.9% vs. 30.3%）。强度的提高主要是由于人工冷却所保留的晶粒细化和局部残余塑性应变。优异的延展性源自精细的 DRX 微观结构和 ED 倾斜双峰织构。