The University of Southampton
University of Southampton Institutional Repository

Ageing and strengthening of cold-rolled Al-Mg(-Cu)-Si-Mn alloys: experimental analysis and modelling

Zhu, Zhihua (2006) Ageing and strengthening of cold-rolled Al-Mg(-Cu)-Si-Mn alloys: experimental analysis and modelling University of Southampton, School of Engineering Sciences, Doctoral Thesis , 301pp.

Record type: Thesis (Doctoral)


Application prospects in the automotive industry have led to increasing studies on Al-Mg- Cu-Si alloys. In this thesis, nine Al-(1-3)Mg-(0-0.4)Cu-0.15Si-0.25Mn (in wt%) alloys with potential applications in packaging and automotive industries have been investigated. By means of mechanical testing, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM), several mechanisms was identified that influence the final strength of cold rolled alloys during ageing: solid solution, work hardening, recovery and precipitation. Microstructure analyses revealed the formation of undissolved particles consuming the small Si addition, which influences age hardening behaviour of the alloys. Tensile testing was performed to evaluate the strength and work hardening. The integrated experimental results showed that for cold worked samples, b² (Mg2Si) contributes to age hardening of Cu-free alloys, whilst both b² and S (Al2CuMg) contribute to that of Cu-containing alloys. According to the experimental findings, a yield strength model has been developed to elucidate the relation between processing and the final strength. It consists of three main components: i) dissolution of intermetallic phase Mg2Si; ii) precipitation of two strengthening phases b² and S; iii) strengthening contributions from solution strengthening, dislocation strengthening and precipitation hardening due to the strengthening phases. The model was calibrated and tested using separate tensile data and was applied to predict the yield strength evolution of cold worked samples during ageing. An accuracy of 8.6 MPa (about 4% of the total range of strengths) has been achieved. Based on the analysis of the relation of work hardening with cold work, composition and ageing time, three primary findings were obtained: i) cold worked samples usually have the lowest work hardening rate (WHR); ii) WHR increases after 30-minute ageing due to recovery and iii) WHR increases with decreasing level of cold work and increasing Mg and Cu contents. Work hardening models based on the Kocks-Mecking (KM) model and the Kocks-Mecking-Estrin (KME) model have been utilized to explain the main trends. The modelling results showed that the KM model is able to predict the work hardening behaviour of cold worked samples reasonably well. However, the KME model is insufficient to fully describe that of cold-worked-and-aged samples.

PDF PhD_thesis-Z_Zhu.pdf - Other
Download (10MB)

More information

Published date: October 2006
Organisations: University of Southampton, Engineering Mats & Surface Engineerg Gp


Local EPrints ID: 64776
PURE UUID: 9b646a80-297d-4091-a96b-8855882b8b25

Catalogue record

Date deposited: 15 Jan 2009
Last modified: 17 Jul 2017 14:12

Export record


Author: Zhihua Zhu
Thesis advisor: Marco Starink

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton:

ePrints Soton supports OAI 2.0 with a base URL of

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.