Experimental investigation on the influence of Mg content on Portevin-Le Chatelier effect in Al-based alloys by using digital image correlation

Abstract

The Protein-Le Chatelier (PLC) effects are investigated by using digital image correlation at a constant applied strain rate of 5.0010-3 s-1 and room temperature in Al-Mg alloys with Mg content values (wt.%) of 2.30, 4.57, 6.10 and 6.91 respectively in this study. Both the yield strength and the ultimate strength increase with increasing Mg content, which is generally called solution strengthening. Type of PLC band changes from A to B with increasing Mg content. In low Mg content (2.30%) alloy, the serration amplitude almost remains 1 MPa, while in each of high Mg content (4.57%, 6.10%, 6.91%) alloys it linearly increases with the strain increasing. The serration amplitude is found to increase with increasing Mg content and gradually reaches a saturated state. With the increase of Mg content, the period of PLC band for continuous propagation gradually reduces and the time when the PLC band location sudden jumps increases in the process of propagation. When the strain is small, the out-of-band deformation of alloy is inhomogeneous obviously. And the deformation inhomogeneity slightly decreases with increasing Mg content. DIC results indicate that the PLC bandwidth does not change with Mg content, while the maximum strain increment in the PLC band increases with increasing both Mg content and strain. Additionally, special periodic damped serrations are observed in the stress-time curve of the low Mg content (2.30%), the corresponding PLC band shows that the periodic changed serrations in the stress-time curve correspond to the transformation of the PLC band orientation. Besides, the PLC band propagates upward continuously both before and after the shift.