Significant improvement in the fracture toughness of 3105 Al sheets under cyclic loading by microstructural evolution through severe-plastic deformation

This research explores the impact of Constrained Groove Pressing (CGP) on the microstructure, mechanical properties, and fracture toughness of 3105 aluminum alloy, under cyclic loading. Employing optical and scanning electron microscopy, it was found that CGP led to grain coarsening, with the average grain size increasing from 30 μm to approximately 50 μm, primarily due to the extended thermal exposure during processing. Elemental mapping revealed the presence of Al6(Fe, Mn)Si and Al6(Fe,Mn) phases, while CGP facilitated a more uniform distribution of finer precipitates. Fractography indicated a shift from a mixed brittle–ductile fracture mode in the as-received material to a predominantly ductile fracture mode in the CGP-processed samples. Mechanical testing showed that while CGP reduced both the tensile ultimate and yield strengths, it significantly enhanced ductility and fracture toughness. The critical stress intensity factor ( K IC ) improved by about 40%, achieving a maximum value of 19.15 . This enhancement in the fracture toughness was attributed to enlargement of the plastic zone at the crack tip, which promoted more uniform stress distribution and increased the energy absorption capacity of the alloy. Statistical analysis revealed that the pressing speed, temperature, the lubricant, number of passes, cooling rate, and the strain path demonstrated certain influences on the fracture toughness of the AA3105 alloy. These findings have implied that CGP could be an effective technique for enhancing the fracture resistance of 3105 aluminum alloy, offering potential benefits for various structural applications.