Quench Sensitivity of AA 7136 Alloy: Contribution of Grain Structure and Dispersoids
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Quench sensitivity of the extruded AA7136 alloy plate specimens with coarse elongated recrystallized grains (CG), fine equiaxed recrystallized grains (EG), and fibrous partial-recrystallized grains (FG) was investigated with the aim to understand the quantitative contribution of grain structure and dispersoids. With the decrease of quenching rate from about 244 °C/s to 1.3 °C/s, the hardness decrement after aging is about 45, 40, and 30 pct, respectively, for the CG, EG, and FG specimens; therefore, quench sensitivity is the highest for CG specimen, intermediate for EG specimen, and the lowest for FG specimen. There are major quenching-induced η (MgZn2) phase and minor T (Al2Zn3Mg3) phase in the slowly-quenched CG, EG, and FG specimens, and a plate-like Y phase occasionally appears in subgrains of the FG specimen. The quantitative contribution to quench sensitivity by grain boundaries, subgrain boundaries, and dispersoids in different specimens is discussed based on the amount of quenching-induced precipitates associated with them.
This work is supported by the National Key Research and Development Program of China (2016YFB0300901), and the Shenghua Yuying Project of Central South University (20130603). The authors would like to thank Dr. Saiyi Li who helped in improving the manuscript.
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