Effect of Post Cryorolling Treatments on Microstructural and Mechanical Behaviour of Ultrafine Grained Al–Mg–Si Alloy

To investigate the effect of post cryorolling treatments on simultaneous enhancement in strength and ductility of ultrafine grained material (UFG), Al 6061 alloy was subjected to cryorolling followed by warm rolling (CR + WR) and compared with cryorolling followed by short annealing (CR + SA) at the same temperature. Transmission electron microscopy (TEM) was used to characterize the microstructural features of the processed material. The mechanical properties were investigated through Vickers hardness testing and tensile testing at room temperature. TEM, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to investigate the precipitation evolution in UFG material. Results indicated that the alloy subjected to CR + WR has shown improved mechanical properties (114 HV, ultimate tensile strength (UTS): 350 MPa) as compared to that in the case of CR + SA (105 HV, UTS: 285 MPa). The size of the precipitates observed in CR + WR sample after peak ageing treatment is finer than that of peak aged CR + SA sample. The UTS of peak aged CR + WR sample (UTS: 390 MPa) was found to be higher than that of peak aged CR + SA sample (UTS: 355 MPa), without decrease in ductility.