The effects of the working temperatures (260 °C, 200 °C and 130 °C) on microstructure formation in the AA 6063 alloy, processed upto ten passes by cyclic expansion extrusion (CEE) was studied. The microstructures of the CEE-processed specimens in the convergent and extrusion regions (center and edge) were examined after every two passes. The EBSD analysis revealed a decrease in the average grain size from 22 ± 5 µm to 2 ± 0.5 µm after four passes, with a simultaneous presence of a large fraction of HAGBs (45%) at 130 °C processing temperature. The TEM observations also confirmed the presence of nano-grains of sizes in the range of 50–100 nm. The CEE-processed specimen showed the highest improvement in hardness and ultimate tensile strength from 38 ± 3.4 HV and 118 ± 6 MPa to 122 ± 1 HV and 267 ± 2 MPa, respectively, after four passes at 130 °C. The specimens processed at 260 °C (ten passes), and 200 °C (four passes) showed moderate improvement in strength of 184 ± 3 MPa and 216 ± 3 MPa, respectively. On further straining (at 200 °C and 130 °C after six to ten passes), continuous dynamic recovery and dynamic re-crystallization took place which led to grain growth during SPD and, as a result, the alloy lost its strain hardening capacity and there was a decrease in the mechanical properties. At higher number of passes, the grains were elongated and coarsened, i.e., a non-equiaxed microstructure was seen after ten passes at 200 °C and 130 °C. In contrast, the specimen processed at 260 °C after ten passes, showed a homogeneous microstructure with near-equiaxed grains with 38% of HAGBs. A lower processing temperature produced a microstructure with a fine grain size distribution after a lower number of passes.

研究了工作温度（260°C，200°C和130°C）对AA 6063合金（通过循环膨胀挤压（CEE）加工多达10道次）的组织形成的影响。每两次通过后，检查收敛和挤压区域（中心和边缘）中经CEE处理的标本的显微结构。EBSD分析显示，经过四道次加工后，平均晶粒尺寸从22±5 µm减小到2±0.5 µm，同时在130°C的加工温度下同时存在大量的HAGB（45％）。TEM观察还证实存在尺寸在50–100 nm范围内的纳米晶粒。经过CEE处理的样品在130°C下经过四次测试后，硬度和极限拉伸强度分别从38±3.4 HV和118±6 MPa分别提高到122±1 HV和267±2 MPa，显示出最高的改善。分别在260°C（十次通过）和200°C（四次通过）下处理的样品的强度分别适度提高了184±3 MPa和216±3 MPa。在进一步应变（在六到十次通过后在200°C和130°C下）时，发生了连续的动态恢复和动态重结晶，这导致SPD期间晶粒生长，结果，合金失去了应变硬化能力，并且机械性能下降。在更高的通过次数下，晶粒被拉长和粗化，即在200°C和130°C进行十次通过后，观察到不均等的显微组织。相比之下，经过十次通过后在260°C下处理的样品显示出均匀的微观结构，晶粒几乎相等，具有38％的HAGB。