effect of constrained groove pressing on anisotropy and formability of al-1050: insights from forming limit diagrams

Constrained groove pressing (cgp) is an effective severe plastic deformation (spd) technique used to strengthen metals by refining their microstructure, resulting in enhanced material strength but reduced formability. the forming limit diagram (fld) is a critical tool for representing the deformability of sheet metals under various loading conditions before necking occurs. despite its significance, the effects of cgp parameters on fld diagrams have not been thoroughly investigated. this study examines the influence of cgp passes on the fld and mechanical properties of al-1050 aluminum sheets. the results reveal that the yield strength increased from 133 mpa after the first pass to 140 mpa and 160 mpa after the second and third passes, respectively. the ultimate tensile strength (uts) initially rose to 185 mpa after the first pass, representing a 26% improvement compared to the as-received material, but then slightly decreased by 3.9% and 4.3% after the second and third passes, respectively. elongation exhibited a sharp 45% reduction following the first pass but improved by 18% in the second and third passes compared to the first pass. these mechanical property trends can be attributed to grain refinement, the evolution of ultra-fine grains, reduced strain hardening, and an increased rate of cell formation during the cgp process. the fld showed a significant 50% reduction after the first pass relative to the as-received condition, but gradually increased with subsequent passes, improving by 8% and 25% after the second and third passes, respectively. furthermore, an increase in the number of passes significantly reduced planar anisotropy variation.