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借助拉伸试验、维氏显微硬度测试、TEM与EBSD等表征手段,研究了限制模压变形道次与变形后退火对纯铝板材微观组织与力学性能的影响规律。经过多道次的限制模压变形,材料晶粒尺寸由初始退火态的约30μm细化至亚微米级,强度、硬度显著提高。在回复阶段变形材料出现退火强化现象,且在300℃退火时仍保持良好的热稳定性。超细晶材料的退火强化现象主要由晶界位错源抑制强化引起,并与退火温度和应变累积量密切相关。材料晶粒组织在变形及退火过程中主要以小角度晶界为主,且应变累积的不均匀性始终存在。变形后期表面微裂纹的出现对材料的力学性能造成不良影响。2道次模压变形板材在300℃下退火1 h后的综合性能最优。
With tensile test, Vickers microhardness test, TEM and EBSD and other means of characterization, the effects of limiting the number of deformation steps and post-deformation annealing on the microstructure and mechanical properties of pure aluminum sheet were studied. After multi-pass molding deformation, the grain size of the material is refined from about 30μm to submicron level in the initial annealed state, and the strength and hardness are significantly increased. During the recovery phase, the deformed material showed the phenomenon of annealing strengthening, and it still maintained good thermal stability when annealed at 300 ℃. Annealing of ultrafine-grained materials is mainly caused by the inhibition of grain boundary dislocations, which is closely related to the annealing temperature and the cumulative amount of strain. In the process of deformation and annealing, the grain structure of the material is dominated by small-angle grain boundaries, and the nonuniformity of strain accumulation always exists. The appearance of microcracks at the late stage of deformation has an adverse effect on the mechanical properties of the material. 2-pass molded deformed sheet annealed at 300 ℃ for 1 h after the best overall performance.