An Extended Age-Hardening Model for Al-Mg-Si Alloys Incorporating the Room-Temperature Storage and Cold Deformation Process Stages

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Web End = OLE RUNAR MYHR, YSTEIN GRONG, and CARMEN SCHFER

In this article, a new age-hardening model for Al-Mg-Si alloys is presented (named NaMo-Version 2), which takes into account the combined eect of cold deformation and prolonged room-temperature storage on the subsequent response to articial aging. As a starting point, the original physical framework of NaMo-Version 1 is revived and used as a basis for the extension. This is permissible, since a more in-depth analysis of the underlying particle-dislocation interactions conrms previous expectations that the simplifying assumption of spherical precipitates is not crucial for the nal outcome of the calculations, provided that the yield strength model is calibrated against experimental data. At the same time, the implementation of the KampmannWagner formalism means that the dierent microstructure models can be linked together in a manner that enforces solute partitioning and competition between the dierent hardening phases which form during aging (e.g., clusters, b and b). In a calibrated form, NaMo-Version 2 exhibits a high degree of predictive power, as documented by comparison with experiments, using both dedicated nanostructure and yield strength data as a basis for the validation. Hence, the model is deemed to be well-suited for simulation of thermomechanical processing of Al-Mg-Si alloys involving cold-working operations like sheet forming and stretch bending in combination with heat treatment and welding.

DOI: 10.1007/s11661-015-3175-y The Author(s) 2015. This article is published with open access at Springerlink.com

I. INTRODUCTION

THE age-hardening Al-Mg-Si alloys achieve their unique mechanical properties through a delicate balance of precipitation hardening, solid solution hardening, and strain hardening.[13] Because the former strength contribution is by far the most important one, the precipitation sequence and resulting strength evolution occurring during natural and articial aging of the alloys have been extensively investigated and reported upon in the scientic literature.[46] In addition, the chemical composition and atomic structure of the clusters and hardening precipitate which form have been studied in detail by means of various...