Effect of Pressing Speed on Al-Mg-Si Aluminium Alloy Processed by Repetitive Corrugation and Straightening

Abstract

Repetitive Corrugation and Straightening (RCS), a promising Severe Plastic Deformation technique (SPD) is used to produce ultrafine grained (UFG) / nanostructured material in coarse grained structure. In this work, Al-Mg-Si aluminium alloy was subjected to RCS process at two different pressing speeds (0.5 and 2.0 mm. sec -1 ) with the RCS die having equal breadth and height of 5 mm and the groove angle (θ) of 30°. The specimens were processed to the maximum of 8 numbers of passes. The microstructural features were studied using TEM. TEM micrographs confirm the formation of dislocation cell in Al-Mg-Si alloy after 8 pass at room temperature processing condition. The sub-grain formation related to the strength. Tensile strength and hardness of the RCSed specimen were studied and compared in order to study the effect of pressing speed on the properties. The strength and hardness were high in the specimen prepared at low pressing speed. The hardness value increased to 86 HV and 96 HV at the end of 8 passes respectively for 1 mm. sec -1 and 0.5 mm. sec -1 respectively, originally form 69 HV. The strength increases in a linear manner with the increase in number of passes. The strength increased to 187 MPa at the end of 2 pass processed with the pressing speed of 0.5 mm. sec -1 and 178 MPa at the end of 6th pass processed with the pressing speed of 2 mm. sec -1 . The unprocessed alloy shows 70 MPa as strength.