Manufacturing induced property development

As the second most widely used structural metal in the world, after steel, Al-alloys have a low density (3 times lighter than steel), high corrosion resistance and a good combination of physical and mechanical properties[1]. In terms of specific strength (strength/density), Al-alloys outperform conventional steels and match the performance of advanced high strength steels (AHSS) developed in recent years. This makes Al alloys particularly attractive for applications in the transport industry. The demand for aluminium products has increased 30-fold since 1950 and this exceptional growth is predicted to continue well into the first half of the 21st century. A large proportion of aluminium products are fabricated using metal forming technologies. Metal forming is not only a net-shape manufacturing process that shapes the final geometry of a component via plastic deformation, but also changes the mechanical properties over the entire volume of the component. The fact that plastic deformation alters the mechanical properties of a component over its entire volume is not yet widely appreciated in the design community [2]. In the conventional design process, the designer develops the component geometry based on specifications of the loading conditions during service and properties of virgin materials. Due to uncertainties, a safety factor significantly greater than 1 is applied to the nominal load, resulting in an increase in both dimensions and weight of the final component. Generally, the manufacturing process is not considered in specifying the material capabilities in the design process although it can substantially alter these capabilities [3]. This provides us with a great opportunity for a holistic integration of component design, manufacturing process and high performance engineering materials.

The main aim of this research project is to establish a fundamental understanding of the effect of metal forming process on manufacturing-induced properties in shaped aluminium components for maximum performance in automotive applications. This involves the study of the efficiency of four simple deformation modes (tensile, compression, shear and torsion) for generating work hardening by determining the stored dislocation density in the deformed material that is responsible for enhanced mechanical strength. This helps to achieve the maximum work hardening (the full potential) of each deformation mode. However, real manufacturing processes are complex and usually involve more than one deformation mode. Therefore, this research project is envisaged to apply the fundamental understanding of manufacturing-induced properties to existing forming processes (eg. roll-bending, stretch-bending, press bending, rotary stretch forming and electromagnetic pulse forming) to understand their potential for generating manufacturing-induced properties.

The research project will study the effect of the different deformation mode, strain path, component geometries and alloy compositions on the resultant microstructure and mechanical properties. This will involve the application of various deformation processing conditions and subsequent materials characterisation using a combination of optical and scanning electron microscopy, together with hardness and tensile testing methods, in order to optimise the maximum practically available strain and deformation-induced strength in automotive aluminium alloys.