Oyindamola Kayode

This paper presents the electrochemical performance and microstructural evolution of friction stir welded joint of dissimilar AA1050 and AZ91D in seawater, for potential applications in the transportation industry. The corrosion behavior of the dissimilar weld was compared to the corrosion behavior of the parent materials, and similar welds of each alloy. The experiments were successfully conducted with an H13 hot‐working tool steel in butt‐joint configuration. The results revealed the presence of intercalated microstructure in the dissimilar weld and homogenous microstructures in the similar welds. The corrosion resistance properties of the parent materials and similar welds were higher than that of the dissimilar weld sample. The dissimilar weld has a current density of 3.83×10⁻⁵ A/cm² and corrosion rate of 9.99×10⁻⁴ mm/year; and is most susceptible to corrosion, due to the galvanic coupling between the dissimilar alloys and intermetallic compounds. The similar weld of AA1050 has a current density of 1.99×10⁻⁷ A/cm² and corrosion rate of 1.44×10⁻³ mm/year, while the similar weld of AZ91D has a current density of 8.58×10⁻⁶ A/cm² and corrosion rate of 1.13×10⁻¹ mm/year.

Lightweight structures are increasingly in demand in the automotive manufacturing industry for fuel economy, vehicle efficiency and meeting reduction in emissions regulations. Weight reduction in automobiles have been achieved traditionally by reducing the body panel steel-sheet thickness and increasing its strength, but this technique is faced with the challenge of reduced stiffness in the panels. In the bid to incorporate numerous light-weighting ideas in manufacturing, the replacement of steel with light metals has been considered. Aluminium and magnesium are alternative materials that could be used to substitute steel because they are both lighter and possess comparable structural characteristics. Aluminium and magnesium has a density of 2.7 g cm⁻³ and 1.74 g cm⁻³ respectively compared to steel density of 7.86 g cm⁻³. However, there is usually unavailability of aluminium for high-volume production. Hence, the joining of aluminium to magnesium in the right proportion could be suitable as potential materials for new automobile applications to mitigate the challenges faced with the usage of steel and availability of aluminium and help to further reduce the vehicle weight. This study focuses on a review of the basis and joining of aluminium and magnesium alloys through friction stir welding to derive insights on appropriate joining process parameters selection.

Molecular dynamics (MD) is a computer simulation method for studying the physical movements of atoms and molecules at nanoscale. It allows interaction between the atoms and molecules for a fixed period, giving an understanding of the system as they dynamically begin to evolve. The paths of the atoms and molecules are determined by numerically solving Newton's equations of motion for a system of interacting atoms, where interatomic potentials or molecular mechanics force fields are used to calculate forces and potential energies between the atoms. In this study, the basic parameters used in MD simulations are briefly discussed. An MD simulation of the friction stir processing (FSP) of aluminium alloy 6061-T6 was carried out to explain the invisible thermodynamic microscopic details which occurred during the process. However, the aim of the MD simulation is not to predict precisely the process, but to predict the average thermodynamic behavior of the process if conducted in a practical state. This is to further enhance the understanding of the FSP process. The results obtained from the MD simulation prove that it may be possible to adequately represent the MD simulation of the FSP of an aluminium alloy.