中文摘要：

研究了纯镁在350℃往复挤压2,4,8道次,以及在250℃,350℃,450℃往复挤压2道次的组织和力学性能的变化规律。结果表明,纯镁经350℃往复挤压后,组织显著细化,挤压道次从2增加到8时,晶粒尺寸无明显变化,而屈服强度下降,延伸率提高。通过电子背散射衍射技术（EBSD）发现纯镁在350℃往复挤压2,4,8道次后,形成{}0001基面与挤压方向分别约成25°,30°,40°夹角的织构,且织构强度增加,基面滑移系的Schmid因子上升。纯镁在250℃,350℃,450℃往复挤压2道次后,随着挤压温度下降,晶粒尺寸减小,屈服强度上升,屈服强度和晶粒尺寸之间的关系可表述为σs=5.4＋338.6d-12。

英文摘要：

Microstructure and tensile property of pure magnesium processed by cyclic extrusion-compression （CEC） at 350℃ for 2, 4 and 8 passes respectively, as well as for 2 passes at 250℃, 350℃ and 450℃ respectively are investigated. Results showed that the microstructure of pure magnesium is signifi- cantly refined and recrystallized after CEC for 2 passes at 350℃. With the increase of passes, the grain sizes of CECed pure magnesium showed no obvious differences. It was found by means of electron back- scatter diffraction （EBSD） analysis that a texture with the basal plane of grains inclining 20° -40° to the extrusion direction developed during the CEC processing. With the increase of CEC passes, the maximum intensity of the texture and Schmid factor of basal slip system increased. Compare to that for 2 passes, the yield stress of pure magnesium after CEC for 8 passes at 350℃ decreases from 60 MPa to 41 MPa, and the elongation increases from 8% to 16.7%. The yield stress and grain size of the pure Mg processed by CEC for 2 passes at 250℃, 350℃ and 450℃ follows the HalI-Petch relationship, which can be described as σ = 5.4 ＋ 338.6d 2.