Abstract

The main goals of this work were to manufacture novel Al–Zn extruded alloys by varying the Zn content (0, 10, 20, 30 wt%), investigate the microstructural evolutions, hot deformation, and work hardening behaviour by hot compression test at different temperatures (25 °C, 75 °C, 150 °C, 225 °C, 300 °C). Al–20Zn alloy microstructure revealed α-Al and uniform distribution of (α + η) phases, coherent (α + η) crystals in GBs with casting defect-free surfaces, and effective interactions of pinning dislocations which led to improve mechanical performance of Al–20Zn alloy, as compared to the other alloys. The observed engineering stress–strain curve results revealed the decrease of stress with increasing of temperature due to flow softening, dynamic recovery and dynamic recrystallization. These results displayed also an increase of stress value with increasing of Zn content due to the precipitation of high density (α + η) phase in the matrix and GBs, increasing of forest and mobile dislocations density with strain fields, and the formation of fine dendrites. Work hardening rate (WHR) of extruded samples displayed three stages: stage I, WHR decreased slightly with increasing of temperature up to 75 °C and decreased drastically from 75 °C to 300 °C due to softening; stage II, WHR maintained constant due to balance between dislocation generations and dislocation annihilation; stage III, WHR slightly increased due to strain hardening of (α + η) phase. WHR was observed to increase considerably with increasing of Zn content due to the formation and dispersion of high density of (α + η) phase in the Al matrix and GBs. Deformation micro-localization in terms of different characteristics was examined and reported on the deformed samples after hot-compression test through SEM micrographs.

Graphic Abstract

中文翻译：

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挤压和热挤压加工新型Al-Zn二元合金的组织演变，热变形和加工硬化行为

摘要

这项工作的主要目的是通过改变Zn的含量（0、10、20、30 wt％）来制造新型的Al-Zn挤压合金，通过不同温度下的热压缩试验研究其组织演变，热变形和加工硬化行为。温度（25°C，75°C，150°C，225°C，300°C）。Al-20Zn合金的显微组织显示出α-Al和（α+η）相的均匀分布，GBs中具有铸造无缺陷表面的相干（α+η）相干晶体以及钉扎位错的有效相互作用，从而改善了Al的机械性能–20Zn合金，与其他合金相比。观察到的工程应力-应变曲线结果表明，由于流动软化，动态恢复和动态再结晶，应力随着温度的升高而降低。这些结果还表明，由于基质和GBs中高密度（α+η）相的析出，应力值随Zn含量的增加而增加，森林和活动位错密度随应变场的增加而增加，并且细小枝晶的形成。挤出样品的工作硬化率（WHR）表现为三个阶段：第一阶段，随着温度升高至75°C，WHR略有下降；由于软化，WHR从75°C急剧下降至300°C。在第二阶段，由于位错世代与位错an灭之间的平衡，WHR保持恒定；在第三阶段，由于（α+η）相的应变硬化，WHR略有增加。观察到WHR随着Zn含量的增加而显着增加，这是由于在Al基体和GBs中形成并分散了高密度的（α+η）相。

图形摘要