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通过光学显微镜、背散射电子衍射分析(EBSD)和室温拉伸试验研究了多道次连续轧制AZ31镁合金板材经200~400℃不同温度退火1 h后晶粒尺寸和微观织构的演化及其与力学性能的关系。结果表明:轧制板材经250℃×1 h退火后,静态再结晶几乎完成,晶粒细小均匀,平均晶粒尺寸约5.5μm,综合力学性能良好,抗拉强度和断后伸长率分别达到261 MPa和26.7%;当退火温度不高于350℃时,退火态板材基面织构较轧态低且差别较小。随退火温度升高,晶粒缓慢长大,晶界取向角分布由<10°和30°双峰连续分布转变为30°单峰连续分布。此时,抗拉强度主要与晶粒尺寸有关。当退火温度达到400℃时,再结晶晶粒发生异常长大,基面织构急剧增强,晶界取向角呈离散分布,导致抗拉强度增加,而伸长率显著降低。
The grain size and microstructure evolution of multi-pass continuous rolling AZ31 magnesium alloy sheets annealed at 200-400 ℃ for 1 h were investigated by optical microscope, backscattered electron diffraction (EBSD) and tensile test at room temperature. Its relationship with mechanical properties. The results show that the static recrystallization of the rolled sheet is almost completed after annealing at 250 ℃ for 1 h, the grains are fine and uniform, the average grain size is about 5.5 μm, the mechanical properties are good, the tensile strength and elongation at break reach 261 MPa and 26.7% respectively. When the annealing temperature is not higher than 350 ℃, the texture of the annealed sheet is lower and less difference than that of the rolled sheet. With the increase of the annealing temperature, the grains grow slowly, and the orientation distribution of the grain boundaries changes from a bimodal continuous distribution of <10 ° and 30 ° to a continuous continuous distribution of 30 °. At this point, the tensile strength is mainly related to the grain size. When the annealing temperature reaches 400 ℃, the recrystallized grains grow abnormally, the texture of the base surface increases sharply, and the orientation angles of the grain boundaries are discretely distributed, resulting in the increase of tensile strength and the decrease of the elongation.