Combined effects of ECAP and subsequent heating parameters on semi-solid microstructure of 7075 aluminum alloy

The combined effects of equal channel angular pressing (ECAP) and subsequent heating to a semi-solid temperature on the microstructural characteristics of the 7075 aluminum alloy were investigated. The microstructure is influenced by several parameters including the number of ECAP passes, ECAP route, consequent heating temperature, and holding time. The effects of these parameters on the microstructural characteristics including grain size and shape factor of the 7075 aluminum alloy were studied using experimental tests and Taguchi method. The results indicate that five-pass ECAP in route BA and subsequent isothermal holding at 630 °C for 15 min are more appropriate for achieving a semi-solid microstructure. The processing route and holding time have the highest impact on the grain size while the number of ECAP passes and heating temperature have the least impact on the grain size. Meanwhile, the shape factor is significantly influenced by the processing route, holding time and heating temperature while it is less influenced by the number of ECAP passes.