Development of Al-Mg-Si-(Cu) Alloys for Automotive Body Panels and the Related Ageing Behaviours

In this work, Al-Mg-Si-Cu alloys for automotive body panels were designed and the related ageing behaviours were discussed in detail to help understand natural ageing and pre-ageing, as well as their influence on the subsequent paint-bake response. The clustering behavior of these Al-Mg-Si-Cu alloys in different ageing conditions was investigated by hardness / yield strength and electrical conductivity testing. The microstructure was investigated by using Electron Backscattered Diffraction (EBSD) technique, along with Scanning Electron Microscopy with Backscattered Electron Detector (BSE). The results show that the paint bake response is strongly influenced by the pre-ageing and natural ageing conditions. Both alloys show serrated yielding in a short natural ageing condition. Immediate high-temperature pre-ageing treatments were found to give a promising hardening response during the subsequent artificial ageing/ paint baking at 170oC.

Modelling the Portevin-Le Chatelier effects in aluminium alloys: a review

Plastic deformation processes are among the most demanding processes in manufacturing because they lead to different microstructure features in the materials produced. Various dislocation patterns can be induced by plastic strain under different conditions. A serrated yielding/jerky flow in some dilute alloys, such as aluminium-magnesium alloys during plastic deformation, is a well-known phenomenon under certain regimes of strain rate and temperature, as reported in a significant number of works. The serrated features in these materials reflect the so-called Portevin-Le Chatelier effects. These undesirable effects are due to the interaction between solute atoms and mobile dislocation during the plastic deformation, which is known as dynamic strain ageing. There are a significant number of theoretical and numerical investigations that have focused on describing the serrated behaviours of these materials during plastic deformation. Hence, the fundamental objective of this paper is to provide a general review of different constitutive modelling in regards this feature. The typical material models and new constitutive models describing this feature are presented. In addition, applications of the models are provided along with their respective advantages and disadvantages.