Investigation of fatigue behavior of Al20Zn-2Cu alloy processed by equal channel angular extrusion (ECAE)

In this study, Al20Zn-(1-5)%Cu alloys were produced by permanent mold casting. Since the alloy containing 2% Cu exhibited the best mechanical performance, the optimal copper ratio was determined to be 2%. The equal channel angular extrusion (ECAE) method, which is one of the severe plastic deformation techniques, was applied to the Al20Zn-2Cu alloy. The microstructure and mechanical properties of the alloy, as well as its fatigue behavior under various routes and number of passes of the ECAE process, were investigated in detail. Significant improvements in the mechanical properties and fatigue performance of the alloy were observed, attributed to the structural changes arising from the ECAE process, the effectiveness of the strain hardening mechanism, and the substantial reduction of casting defects (porosity). Specifically, after three passes of ECAE, an approximate increase of 59% in fatigue strength limit and 62% in impact toughness was achieved. Furthermore, the effects of ECAE parameters such as the number of passes and process routes on the structural and mechanical properties, especially fatigue behaviour of the alloy were investigated. The examinations revealed that the ECAE process completely eliminated the typical dendritic casting structure containing porosity and resulted in a microstructure consisting of fine and ribbon-like elongated grains in route-A, whereas route-BC exhibited a coarser and more intermingled structure. It was observed that the fatigue strength and fatigue life of the alloy increased with the number of passes due to the structural changes, and the values were higher in route-BC compared to route-A. In addition, the relationships between the structure and mechanical properties of the alloy and its fatigue behavior were studied in detail. As a result of these investigations, it was determined that the fatigue properties are most closely related to impact toughness.