Effect of ECAP temperature on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy

The effect of equal channel angular pressing (ECAP) at different temperatures (room temperature, 120, 150 and 180 degrees C) on microstructure and mechanical properties of Al-7075 solid solution alloy was investigated. Microstructure of the specimens was examined using orientation imaging microscopy, transmission electron microscopy as well as X-ray diffractometer, and mechanical properties were measured by Vickers microhardness and tensile tests. Microstructural investigations showed that after 3 or 4 passes of ECAP, fine grains with average grain sizes in range of 300-1000 nm could be obtained at different ECAP temperatures. Increasing ECAP temperature from 120 to 180 degrees C caused a decrease in mechanical properties as a result of increasing grains and precipitates sizes, decreasing fraction of high angle boundaries and also transformation of it into 11 phase, while increasing ECAP temperature from RT to 120 degrees C leads to an increase in mechanical properties due to the formation of small it precipitates. So it can be concluded that ECAP process at 120 degrees C is the optimum process for attaining maximum mechanical properties. Quantitative estimates of various strengthening mechanisms revealed that the improvement of mechanical properties was mainly attributed to grain refinement strengthening, precipitation strengthening and dislocation strengthening. (C) 2016 Chinese Materials Research Society. Production and hosting by Elsevier B.V.