Abstract Age-hardenable aluminium 7XXX alloy sheets represents a very attractive material for the aerospace field; however, their limited formability at room temperature restricts their adoption in the industrial context. In the present study, deformation of AA7075 sheets at temperatures lower than the room one is presented as a possible strategy to overcome this limitation. To this aim, a comprehensive experimental campaign was carried out on AA7075 sheets in peak aged condition at varying temperature and triaxiality states. Specifically, the temperature was changed from −100 °C to 300 °C whereas different stress triaxialities states were achieved by adopting different specimen configurations, namely smooth, notched and shear. A necking locus curve was presented and modelled. Results show that, regardless of the stress state, the uniform elongation monotonically increased as the testing temperature was reduced, favouring material formability. Microstructural and mechanical investigations carried out on the deformed samples revealed that deforming at temperatures higher than the room one drastically increased the number of coarse intermetallic particles. On the contrary, sub-zero deforming temperatures favoured the intermetallic particle fragmentation and the formation of high density of precipitates and dislocations.

中文翻译：

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AA7075铝合金亚零温薄板冲压加工的力学和显微组织行为

摘要 时效硬化铝 7XXX 合金板是航空航天领域极具吸引力的材料；然而，它们在室温下的有限成型性限制了它们在工业环境中的采用。在本研究中，AA7075 板材在低于室温的温度下的变形被认为是克服这一限制的一种可能策略。为此，我们对 AA7075 板材在不同温度和三轴状态下处于峰值时效状态进行了全面的实验活动。具体来说，温度从-100°C 变为 300°C，而通过采用不同的试样配置，即平滑、缺口和剪切，实现了不同的应力三轴状态。呈现并建模了颈缩轨迹曲线。结果表明，无论压力状态如何，随着测试温度的降低，均匀伸长率单调增加，有利于材料的成型性。对变形样品进行的微观结构和机械研究表明，在高于室温的温度下变形会显着增加粗金属间化合物颗粒的数量。相反，低于零的变形温度有利于金属间化合物颗粒的破碎和高密度析出物和位错的形成。