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The effect of sensitisation on 5xxx series aluminium alloys
thesisposted on 23.02.2017, 23:15 by Zhang, Ruifeng
Aluminium (Al) and its alloys represent the commodity ‘light metals’ and have had continued usage and intense interest from industry and the academic field since their large-scale industrial implementation commencing approximately 100 years ago. Various properties can be achieved in Al-alloys which arise from alloying with many other elements. Al-alloys can provide corrosion resistance, formability, weldability, strength and damage tolerance; however the actual combination of such properties is nominally a trade-off. As a result a wide range of carefully engineered Al-alloys are applied across different fields. This includes shipbuilding, where density, weldability, and corrosion resistance are key properties. Despite the advantages of Al-alloys in marine applications, severe intergranular corrosion (IGC) damage can take place after a prolonged service time at elevated temperature. This concern originates from a supersaturation of magnesium (Mg) in the common marine alloys (based on the Al-Mg system) which can form deleterious anodic Mg2Al3 β-phase) particles at grain boundaries. Herein, this process is termed “sensitisation” as it reflected a detrimental microstructural evolution. Although the β-phase evolution is the main factor for sensitisation induced damage, there are yet to be any critical studies on microstructural evolution prediction (experiment or modelling), in a deterministic sense. This project aims to cover the various principal factors that dictate microstructure and the influence upon intergraular corrosion from sensitisation. This is done with the view towards a science-based tangible and practical reversion heat treatment to repair sensitised Al-Mg alloys.