The Bauschinger Effect and The Work Hardening of Aluminum Copper Alloys

Abstract

<p>Several conflicting models have been proposed to describe the work hardening behaviour of alloys composed of a hard second phase in a plastically deforming matrix. Good agreement is reported when the models are compared with the results of unidirectional tests. To distinguish between the models, it is necessary to use tests which include deformation in both the forward and reverse directions.</p> <p>In this study the work hardening behaviour in aluminum copper alloys has been studied using deformation in compression immediately after deformation in tension. The large Bauschinger Effect obtained has been analysed to give the magnitude of the long range back stress present in the alloy due to the elastic deformation of the θ' particles in the plastically deforming matrix. Experiments were carried out on polycrystals, and on single crystal test pieces oriented for single and multiple slip over a wide range of temperatures. The results give excellent agreement with a model which calculates the long range back stress. The reported good agreement of other experimental work with an opposing model has been critically examined.</p> <p>The behaviour at large strains has been studied to determine the processes leading to plastic relaxation. The conditions at the onset of necking of the single crystal test pieces have been examined, and the formation of coarse shear bands and final fracture correlated with the work hardening rate.</p>