Grain Boundary Sliding and Strain Rate Sensitivity of Coarse and Fine/Ultrafine Grained 5083 Aluminum Alloys

International audienceThe viscoplastic behavior of coarse and bimodal fine/ultrafine grained (F/UFG) Al5083 alloywas investigated between 20 °C and 200 °C through tensile tests at various strain rates, andstress relaxation tests to deduce the strain rate sensitivity (SRS). The plastic strain fields weremeasured by correlation of SEM images. In the F/UFG material at high temperature, very highstrains were measured in shear bands which sometimes crossed the whole gage width andexhibited intensive grain boundary sliding (GBS). Both the SRS and ductility rose with thetemperature, and as the strain rate decreased, mainly due to a rising contribution of GBS, whichaccommodated a much larger fraction of the global strain in the F/UFG material. Theboundary between the temperature–strain rate domains where grain refinement led either tostrengthening or to softening was determined. Finite element simulations of tension andrelaxation tests with viscoplastic grains and sliding grain boundaries captured the macro-scalebehavior of the F/UFG material. It also provided some insight into the mechanisms ofcorrelated and cooperative GBS and grain rotation along percolation paths (both inter andintragranular), probably, responsible for macro shear banding