Theme 2 Joining Advanced Alloys and Dissimilar Materials
Theme 2’s main aim is to develop the underpinning metallurgical science required to support cost effective routes for joining advanced high strength light alloys and multi-material structures. Key areas requiring solutions include; the poor weldability of high strength alloys, interfacial reaction between dissimilar metals, thermal damage, distortion and residual stress, as well as the issues associated with manufacturing metalcomposite hyper joints. Theme 3 will also contribute through improving the knowledge of tailoring oxide films on metal surfaces for improved adhesion and investigating the protection of dissimilar material joints, where galvanic coupling is a major issue.
| The dissimilar metal combinations required by industry, e.g. Al-steel, Mg-Al, Al-Ti, are very difficult to join by traditional fusion welding methods. We have thus focused on low energy friction joining processes for dissimilar metal combinations and advanced surface engineering to facilitate adhesive bonding and composite to metal joining (Theme 3). Solid state friction welding techniques are highly efficient and have the advantage of far greater weldability and reduce the risk of interfacial reaction when welding dissimilar materials. New advances in welding technology with proven potential for success are being targeted, such as friction stir spot welding (FSSW), and high power ultrasonic spot welding (USW), in conjunction with selected fusion welding techniques such as laser conduction spot and conventional laser seam welding. |  |
A key aspect of the theme is to develop models to predict the microstructure and mechanical behaviour of welds in highperformance multicomponent alloys. We are also trying to better understand the factors that affect the metallurgical interactions between dissimilar metals in welding, so that we can use thermodynamic principles to help inhibit detrimental interactions, such as the formation of brittle intermetallic layers at the weld interface.
The research has been targeted at under pinning the following application areas:
- Energy efficient joining of Mg and Al in automotive bodies
- Friction welding advanced alloys for aerospace structures with new welding techniques
- Friction welding dissimilar metal combinations requiring control of bond formation and interfacial reaction (e.g. Al to galvanised steel, Ti to Al)
- Low heat input laser welding light alloys and dissimilar metals
- High performance metal-composite joints; facilitated by manufacturing mechanical locking features on the metals surface to increase shear transfer (so called hyper-joints)
- The surface engineering to facilitate adhesive bonding (theme 3)
- Modelling joint performance through linking process models to microstructure and weld zone property predictions
- Microstructure optimisation of additive layer manufacturing higher performance aerospace components
Examples of Current Projects
- Assessment of the Advantages of Static Shoulder FSW for Joining Aluminium Aerospace Alloys
- Critical Assessment of Welding Techniques for Dissimilar Joining of Aluminium to Steel
- Modelling and Controlling Interfacial Reaction in Dissimilar Metal Welding
- Modelling of Blast Performance of Welded Aluminium Structures in Military Vehicles
- Optimisation of Ultra-Short Cycle Friction Stir Spot Welding
- Predicting Heterogeneity and Defects in Additive Manufacturing
- Predicting Stir Zone Grain Size in Friction Stir Welding and Processing
- Surface Engineering Metal-Composite Hyperjoints