基于往复挤压的7034铝合金形变热处理强韧化机理研究

Study on the Strengthening and Toughening Mechanisms of 7034 Aluminum Alloy Subjected to Reciprocating Extrusion Based Thermo-Mechanical Treatment

摘要:

为提高7034铝合金微观组织均匀性和综合力学性能,本文开展了往复挤压剧烈塑性变形工艺与固溶时效制度的优化设计研究,并表征了不同变形-热处理方案下材料力学性能、晶粒与第二相尺寸分布、位错组态演化的定量规律,建立了塑性变形和热处理制度与7034铝合金的微观组织和力学性能的关联关系。结果表明：经过三道次往复挤压,平均晶粒尺寸由初始态的59μm细化到9μm,平均晶粒尺寸标准差从一道次的3.05下降到三道次的0.8；相较于双级固溶时效,单级固溶时效处理后的MgZn₂相尺寸更细小,密度更高,且多为半共格的η′相,位错塞积演变为亚晶,二者交互作用更强,起到更好的强化效果。最优热处理制度为单级固溶+单级时效,在此条件下,抗拉强度与延伸率分别达到747MPa和4.3%,优于双级固溶+双级时效制度。

Abstract:

In order to improve the uniformity of microstructure and comprehensive mechanical properties of 7034 aluminum alloy, this paper carried out the optimization design of the severe plastic deformation process and solution and aging treatment based on the reciprocating extrusion, characterized the mechanical properties of the material, the size distribution of grain and secondary phase and the quantification of dislocation configuration evolution, established the relationship between plastic deformation and heat treatment and the microstructure and mechanical properties of 7034 aluminum alloy. The results show that, the average grain size is refined from 59μm to 9μm, and the standard deviation of the average grain size decreases from 3.05 to 0.8 after three passes reciprocating extrusion; Compared with the two-stage solution and aging treatment, the MgZn₂ phase after single-stage solution and aging treatment is smaller in size, higher in density, and mostly semi-coherent η" phase, and the dislocations pile-up becomes in sub-grain. The interaction between the two is stronger and the strengthening effect is better. The optimal heat treatment system is single-stage solution + single-stage aging. under this condition, the tensile strength and elongation reach 747MPa and 4.3% respectively, which are better than the two-stage solution + two-stage aging system.