基于数字图像相关法的Mg含量对Al合金Protein-Le Chatelier效应影响的实验研究

利用数字图像相关法研究了常温与恒定应变率(5.00×10~(-3)s~(-1))下Mg含量(质量分数)分别为2.30%,4.57%,6.10%及6.91%四种Al-Mg合金Portevin-Le Chatelier(PLC)效应的宏观变形行为.实验发现,Mg含量的增加导致强化效果的增强;低Mg含量(2.30%)合金中锯齿跌落幅值基本保持不变,而在高Mg含量(4.57%,6.10%,6.91%)合金中随应变增加而增加.锯齿跌落幅值随Mg含量增加而逐渐增大,在高Mg含量合金中趋于饱和.宏观局域变形带的观察结果表明PLC带宽不随Mg含量或者应变改变而变化,带内变形量随着Mg含量或者应变的增加而逐渐增大.此外,在低Mg含量合金的加载曲线后段(应变约为0.3时)观测到了特殊的周期性的衰减锯齿,相应的时域PLC带演化表明加载曲线的周期性转变大锯齿对应着空间上PLC带的转向,幅度逐渐减小的振荡对应着PLC带的传播,且在转向前后PLC带均向上连续传播.

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

The Protein-Le Chatelier (PLC) effects are investigated by using digital image correlation at a constant applied strain rate of 5.00×10^-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.