The linear friction welding process is currently commercially used solely to produce titanium alloy aeroengine bladed disks (blisks). The process can, however, be potentially used to produce welds in non-aeroengine materials for non-aeroengine applications. The aim of this thesis was therefore to demonstrate the capabilities of the process to join materials not commonly used in the aeroengine industry and to develop understanding of the process.The focus of this thesis has been on the linear friction welding of 316L stainless steel and the linear friction welding of dissimilar materials: aluminium to copper, aluminium to magnesium and aluminium to steel. For all of these studies it was seen that weld line and near weld line microstructure could be altered by the use of different welding parameters. This property of linear friction welding was used to advantage to optimise microstructures in dissimilar welds. Intermetallic formation is usually a major challenge to the achievement of welds with good mechanical properties, and for work in this thesis welding parameters were optimised to allow welds with limited intermetallic formation.The welding of 316L and the dissimilar welding of aluminium to copper proved viable. For the welding of 316L and aluminium to copper, fracture during tensile testing occurred in the parent material (aluminium parent material for aluminium to copper). The welding of aluminium to magnesium and aluminium to steel showed promising results, with weld strength comparable to the aluminium parent material for aluminium to steel and comparable to the parent materials in O temper for aluminium to magnesium. However, repeatability of mechanical properties was poor for these dissimilar welds, which would be a significant barrier to commercial exploitation. Further work needs to be conducted to improve repeatability. Weld microstructures were characterised using optical and scanning electron microscopy as well as electron backscatter diffraction and X-ray diffraction techniques.