The grain size dependence of flow stress in a Cu-26Ni-17Zn alloy

The effect of grain size in the range 15-120 mu m on flow stress was studied at room temperature to investigate the Hall-Fetch relationship in a Cu-26Ni-17Zn alloy. It was found that the Hall-Fetch relation is valid for the alloy. The Hall-Fetch constants, sigma(o epsilon) and k(a) are related to true strain (epsilon) in such a way that sigma(o epsilon) is proportional to epsilon and k(epsilon) to epsilon(1/2). An equation for flow stress as a function of true strain and grain size has been derived from these results. Dislocation density model for grain size strengthening is found valid for this alloy. Solid solution strengthening in the Cu-26Ni-17Zn alloy is attributed to the interaction of nickel and zinc atoms with screw dislocations and the effective interaction is more due to modulus mismatch than size misfit. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.