**Sipokazi Mabuwa \* and Velaphi Msomi**

Faculty of Engineering and the Built Environment, Cape Peninsula University of Technology, P.O. Box 1906, Bellville 7535, South Africa; msomiv@gmail.com

**\*** Correspondence: sipokazimabuwa@gmail.com; Tel.: +27-219538778

Received: 18 October 2019; Accepted: 10 December 2019; Published: 17 January 2020

**Abstract:** There is an increase in reducing the weight of structures through the use of aluminium alloys in different industries like aerospace, automotive, etc. This growing interest will lead towards using dissimilar aluminium alloys which will require welding. Currently, tungsten inert gas welding and friction stir welding are the well-known techniques suitable for joining dissimilar aluminium alloys. The welding of dissimilar alloys has its own dynamics which impact on the quality of the weld. This then suggests that there should be a process which can be used to improve the welds of dissimilar alloys post their production. Friction stir processing is viewed as one of the techniques that could be used to improve the mechanical properties of a material. This paper reports on the status and the advancement of friction stir welding, tungsten inert gas welding and the friction stir processing technique. It further looks at the variation use of friction stir processing on tungsten inert gas and friction stir welded joints with the purpose of identifying the knowledge gap.

**Keywords:** friction stir welding; tungsten inert gas welding; friction stir processing; dissimilar aluminium alloys joints; dissimilar metal joints
