Internal Stress in Al and an Al-Mg Alloy Deforming at High Temperatures

In examining the applicability of the dip test to measure the contribution of long range internal stress, it is found that the test can, for any internal stress distribution, be applied to the case where the dislocation velocity is propotional to the effective stress, or else the knowledge of the internal stress distribution is indispensable for the application. Further an extrapolation method is proposed to minimize the error introduced during the time necessary for the dip test. By applying this method and the above theoretical prediction to the high temperature deformation of high-purity aluminium and Al-5.7 at%Mg, it is found that the internal stress is the main component of the flow stress in pure aluminium, while the frictional stress contribution is as large as that of the internal stress in the Al-Mg alloy.