In this work, friction surfacing (FS) of AA5083 on a DH36 steel substrate was experimentally studied. The process parameters such as rotation speed, travel speed and feed rate are of great significance to the success of the FS process. Seven friction surfaced plates with different combinations of parameters were examined. Optical microscopy, SEM and EDS were used to analyse the characteristics of the microstructure and composition of the interface between the surface and the substrate. The results show that the deposition surface quality decreased as the feed rate, travel speed and axial force increased. However, the bond strength increased with higher feed rate, higher rotation speed and lower travel speed. Elemental diffusion of Fe to AA5083 was established, and the intermetallic compound FeAl₃ was produced in the interface.

In the present study, 6 mm nominal thickness dissimilar steel plates were joined using friction stir welding. The materials used were duplex stainless steel and low alloy structural steel. The weld was assessed by metallographic examination and mechanical testing (transverse tensile and fatigue). Microstructural examination identified four distinct weld zones and a substantially hard region within the stir zone at the base of the weld tool pin. Fatigue specimens demonstrated high level fatigue life and identified four distinct fracture modes.

The design life of welded structures and components extends into the very high cycle fatigue (VHCF) regime across various applications. However, the availability of data on the fatigue behaviour of welded joints in the VHCF regime is limited, particularly when compared to the low and high cycle fatigue regimes. The development of ultrasonic fatigue testing equipment has accelerated fatigue testing and allowed for the VHCF properties of welds to be investigated in a feasible timeframe. In the present review, the emerging research concerning the VHCF behaviour of welds of various steels and non-ferrous alloys are individually explored. Overall, it is observed that welded joints have significantly lower fatigue strength than the base metal in the VHCF regime and that welding defects have a considerable influence on fatigue strength. Through the discussion of the relevant literature, important findings concerning the effects of specimen geometry and fatigue improvement methods are underlined. Furthermore, the guidance provided within design standards is compared, and some examples of VHCF failures of in-service components are highlighted. Finally, perspectives on future directions of investigation are put forward with the aim of encouraging further research in the field of VHCF of welds.