Effect of the cyclic expansion-extrusion (CEE) process on mechanical properties and the grain refinement of AA6061 aluminum alloy

In this work, the cyclic expansion-extrusion (CEE) process for aluminum alloy AA6061 is due to its wide industrial applications. First, The CEE process is performed to create a fine stable grain size for the studied alloy. The microhardness of the deformed samples was determined to evaluate the effect of the CEE process on the mechanical properties of the alloy. The average microhardness of the deformed samples increased sharply after 1 CEE cycle from 40Hv to 65Hv or 68Hv. It is particularly noticeable that in subsequent cycles, the average microhardness of the samples hardly changes (Hv ≈ 70). Subsequently, the microstructural survey was conducted to determine the average grain size of deformed samples. The average grain size reached about 5 ÷ 6 µm from the initial value of 100 μm after four CEE cycles. The results show that the effect of the cumulative strain of the CEEed samples significantly on the mechanical properties as well as for the grain refinement to create ultrafine grains (UFGs) in microstructures of the AA6061 alloy.