GENERAL EXPRESSION OF THE ZENER-HOLLOMON PARAMETER AS A FUNCTION OF THE CHEMICAL-COMPOSITION OF LOW-ALLOY AND MICROALLOYED STEELS

Using torsion tests the Zener-Hollomon parameter has been determined i n a selection of 18 steels with compositions appropriate for the study of the influence of each alloying element (C,Mn,Si,Mo,Ti,V,Nb) on the Zener-Hollomon parameter (epsilon over dot exp(Q/RT) = A(sinh alpha s igma(p))(n)). It is demonstrated that all the alloying elements influe nce, to a greater or lesser extent, the activation energy (Q). A rise in the content of any alloy was found to increase the activation energ y, except in the case of carbon which has the opposite effect. An expr ession is given for Q as a function of the content of each alloying el ement and the second side of the equation is completed by determining the optimum values of alpha and n for all the steels, giving 0.01187 M Pa(-1) and 4.458, respectively. It is demonstrated that A is not a con stant but is a function of the activation energy. In this way it is po ssible to calculate the peak stress (sigma(p)) at any temperature and strain rate for any low alloy or microalloyed steel in the austenite p hase. This study brings a new dimension to the Zener-Hollomon paramete r and potentially improves its applications, for example in the calcul ation of stress-strain curves.