On the mechanical behavior of an Al 7075 alloy deformed by asymmetrical and conventional rolling

ABSTRACT Samples of the Al 7075 naturally and artificially aged were processed by conventional and asymmetrical rolling with 5% of thickness reduction. The rolling processes were evaluated under room temperature and under warm condition (130°C). Mechanical properties were evaluated by uniaxial tensile and Vickers microhardness tests. Microstructure evolutions were followed by optical microscopy analysis. Naturally aged samples showed better yield strengthening under warm processing. Greater ultimate stress and ductility under room temperature processing was also noticed in naturally aged specimens. Artificially aged samples showed better mechanical properties under room temperature, softening under warm processing due to grain recovery process. Microhardness tests showed expected results for both rolling types, especially on asymmetrical rolling with the higher predictions were observed. Micrographs have shown no expressive grain changes or refinement although its flattening was observed. Precipitates were analyzed by EDS/SEM revealing the presence of MgZn2 and CuMgAl along the matrix that provides plastic strengthening.

摘要：本研究对经自然时效与人工时效处理的7075铝合金（Al 7075）试样，分别采用常规轧制与压下率为5%的不对称轧制工艺进行加工。轧制过程分别在室温与温热条件（130℃）下开展性能评估。通过单轴拉伸试验与维氏显微硬度试验表征试样的力学性能，借助光学显微镜分析追踪微观组织演变规律。结果表明，温热轧制条件下自然时效试样展现出更优异的屈服强化效果；室温轧制条件下，自然时效试样同样具备更高的极限应力与塑性。人工时效试样在室温轧制条件下力学性能更优，而温热轧制条件下因晶粒回复过程出现软化现象。维氏显微硬度试验结果与两种轧制工艺的预期相符，尤其在不对称轧制中观测到了更高的硬度值。显微图像显示，尽管晶粒出现扁平化现象，但未出现显著的晶粒变化或细化。通过EDS/SEM对析出相进行分析，结果显示基体中存在MgZn₂与CuMgAl相，此类析出相可提供塑性强化效果。