Effect of Various Retrogression Regimes on Aging Behavior and Precipitates Characterization of a High Zn-Containing Al–Zn–Mg–Cu Alloy
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In the present work, the influence of various retrogression treatments on hardness, electrical conductivity and mechanical properties of a high Zn-containing Al–Zn–Mg–Cu alloy is investigated and several retrogression regimes subjected to a same strength level are proposed. The precipitates are qualitatively investigated by means of transmission electron microscopy (TEM) and high-resolution transmission electron microscopy techniques. Based on the matrix precipitate observations, the distributions of precipitate size and nearest inter-precipitate distance are extracted from bright-field TEM images projected along 〈110〉Al orientation with the aid of an imaging analysis and an arithmetic method. The results show that GP zones and η′ precipitates are the major precipitates and the precipitate size and its distribution range continuously enlarge with the retrogression regime expands to an extent of high temperature. The nearest inter-precipitate distance ranges obtained are quite the same and the average distance of nearest inter-precipitates show a slight increase. The influence of precipitates on mechanical properties is discussed through the interaction relationship between precipitates and dislocations.
KeywordsAl–Zn–Mg–Cu alloy Retrogression and re-aging treatment Precipitate Mechanical properties
This study was financially supported by the National Key R&D Program of China (Nos. 2016YFB0300803, 2016YFB0300903).
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