Microstructural Design for Improved Mechanical Behaviour of Advanced Materials
J. Phys. IV France 10 (2000) Pr6-151-Pr6-156
Strain hardening rate in relation to microstructure in precipitation hardening materialsA. Deschamps1, S. Esmaeili2, W.J. Poole2 and M. Militzer2
1 LTPCM/ENSEEG, Domaine Universitaire, BP. 75, 38402 Saint-Martin-d'Hères cedex, France
2 Department of Metals and Materials, University of British Columbia, Vancouver, BC V6T 124, Canada
The influence of microstructure on strain hardening is studied through Kocks-Mecking plots in a number of systems showing precipitation hardening : Al-Zn-Mg, Al-Mg-Si-Cu, and Fe-Cu. The presence of a supersaturated solid solution is shown to result in an extremely high work hardening rate, due to dynamic precipitation during the straining. When precipitation occurs, a drastic change in the work hardening capability is observed, which can be related to the type of precipitate-dislocations interactions and to the residual solute content. Shearable precipitates do not seem to influence greatly the work hardening behavior, which is then mostly controlled by the solute content. Non-shearahle precipitates induce a high initial hardening rate. However this high initial value cannot be sustained to high strains due to extensive dynamic recovery in the solute-depleted matrix. From the analysis of the work hardening rate, it seems that precipitates remain shearable up to very large sizes and to very overaged States in the Al-Mg-Si-Cu and the Fe-Cu alloys, which has important consequences on the modeling of the hardening curve of these alloys.
© EDP Sciences 2000