采用显微硬度测试、拉伸实验、EBSD和TEM等检测手段研究了不同变形量对形变和时效结合制备的Al-Mg-Si-Cu合金力学性能和显微结构的影响. 结果表明, 随着变形量的增加, 轧制态合金的硬度会逐渐增加, 后续时效过程中形变合金均能进一步强化但时效硬化能力逐渐下降; 晶粒沿着轧制方向逐渐被拉长为层状结构, 形成大量亚晶界. 变形量小时, 合金内位错密度随着形变量的增加而增加; 变形量较大时, 位错发生缠结并形成亚晶. 形变导致的位错组态变化显著影响合金的析出特性, 析出相逐渐从离散分布演变为连续分布, 连续分布的析出相是溶质原子析出与缺陷退化交互作用的结果, 通过调整形变量和时效工艺有助于制备强度和塑性结合良好的铝合金.

The 6××× series aluminum alloys Al-Mg-Si-Cu are widely used in the transportation and building industries due to their comprehensive mechanical properties, adequate formability, high corrosion resistance and good weldability. For decades, ultrafine grain structure (UFG) produced by severe plastic deformation (SPD) has been proved to be a promising way in strengthening Al alloy materials. Although this method can guarantee a great improvement in strength, the obtained ductility is always disappointing. Besides, this method has a limitation to fabricate products suitable for practical use. Recently, combining deformation and aging has been proposed to produce high-strength Al alloys. This strategy is very effective in achieving Al alloys with strength-ductility synergy even through conventional producing process, for example, rolling and aging. The strain ratio of deformation is critical in tuning the mechanical properties which could be acquired by the above method. The effect of deformation strain ratio on the age-hardening behaviors and microstructure in Al-Mg-Si-Cu alloy produced by combining cold-rolling and aging are investigated using hardness test, tensile test, EBSD and TEM in this work. The results show that the as-rolled hardness increases gradually with deformation strain ratio. The age-hardening potential declines with the increase of strain ratio, though post-aging could further strengthen the as-rolled alloys. The grains elongate along the rolling direction during deformation and finally have a lamellar structure. Fragmentation and extensive defects like sub-grain boundaries occurs inside the grains. The dislocations become denser inside the alloy with the increase of the deformation ratio. When the deformation ratio is large (above 60%), formation of dislocation tangling and sub-grains are observed. Deformation-induced change of the dislocation configuration affects the precipitation significantly. Due to the interaction between solutes precipitation and defects annihilation, the distribution of precipitates undergoes a change from being isolated to a continuous manner.