Response of the electron work function to deformation and yielding behavior of copper under different stress states

Abstract

The high sensitivity of the electron work function (EWF) to surface condition has attracted increasing interests from materials scientists and engineers. In this study, using a scanning Kelvin probe changes in the EWF of copper under various loading condition and stress states were investigated. Experimental results showed that the tensile strain decreased the EWF in the elastic deformation range, while compressive strain increased the EWF. However, the EWF in the plastic deformation range always decreased with plastic strain no matter it was tensile or compressive. As shown by the simultaneous measurements of the EWF under conditions of plane stress states, yielding point can be related to the critical stress for the transition of the EWF from smooth variation to steep variation, which strongly depended on stress states. It was therefore demonstrated that Kelvin probing technique could be used for determining the onset of yielding since the EWF was a parameter sensitive to yielding process. The Kelvin probing has appeared to be a very promising method for characterizing the yielding behaviors under complex stress states for both homogeneous and inhomogeneous materials. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)