## 2 Review Available Literature
### AA5083-Based MMCs
The bend-ductility test was used to assess the cold formability of FSPed aluminium metal matrix composites. Carbon-nanotube-containing composites fractured under bending, whereas boron-carbide-containing composites survived; hybrid composites cracked, but the crack was less than nanotube-only composites. Poor interfacial nanotube or aluminium bonding and insufficient nanotube dispersion are two possible explanations. The cold formability of the composites is determined by their mechanical and microstructural properties. The B4C-reinforced composite increased tensile strength and hardness by 28 percent and passed the bend ductility test with no surface cracks. The MWCNT-composite reduced fracture strain by 50% while also improving the hardness and tensile properties. The bend-ductility test reveals fractures caused by the CNT clusters that developed in the TMAZ, since it is a single pass FSP. While fracture strain was decreased by 16%, tensile strength and hardness were also increased by 10% and 5%, respectively. This specimen failed the bend-ductility test due to weak MWCNT and aluminium alloy interfacial bonding and insufficient MWCNT dispersion in the composite. [PERSON] et al. [49] studied the wear and mechanical properties of an AA5083-ZrO composite made using FSP. Multi-pass FSP with zirconia nanoparticles was used to fabricate surface nanocomposites on AA5083 sheets in this investigation. The specimen's microhardness, microstructure, wear parameters, and tensile strength were all studied with the number of passes. Following many trial and test runs, it was determined that a traverse speed of 50 mm/min and a rotation rate of 800 rpm, which was also similar to reference [50], was the most suited in terms of possible flaws. These rates were utilized for all FSP passes. For all samples, the tool tilt angle concerning the workpieces was around 3\({}^{\circ}\). As a result, it was discovered that FSP iteration consistently increases the material's tensile strength and microhardness. This was primarily brought about by the FSP-enhanced microstructural modification, which included better powder dispersion, smaller grains, and fewer clustered particles. The eight-pass friction stir processed nanocomposite was subjected to EBSD and TEM examination, which revealed a large number of high-angle grain boundaries as well as ongoing dynamic recrystallization. Wear tests showed that the further processed sample's wear rate was much lower than that of the base material. Furthermore, the fracture surface of the eight-pass treated material, such as the base material, showed ductile fracture with dimples and voids. With a microhardness of 140 Vickers, the composite with eight passes had the most grain-refined structure. In addition, the wear rate of composites generated in eight passes was lowered. [PERSON] et al. [51] used FSP to evaluate the impact of FSP spacing on the growth of B4C- and MWCNT-reinforced AA5083 composite. In this work, FSP was used to add boron carbide and carbon nanotube particles into AA5083 to create hybrid surface composites. Using a single-pass approach, the impact of metal loss in cavities made to contain reinforcements at 8- and 10-mm inter-cavity spacings were examined. A single pass of FSP was run at a 2\({}^{\circ}\) tilt angle, 16 mm/min traverse speed, and 750 rpm rotating speed to prepare surface composites. Surface composites with individually reinforced B4C and MWCNT particles, as well as a hybrid composite with both reinforcements, were created. Microstructural analysis and an examination for the existence of any flaws were carried out using optical microscopy and SEM. Mechanical tests found that composites with 10-millimetre inter-cavity spacing and boron-carbide particles increased their UTS and microhardness by up to 38% and 18%, respectively. The cold formability of FSPed composites was then evaluated using the U-bend ductility test. Due to severe cracking brought on by clustering and insufficient material-loss compensation, carbon nanotube composites with an inter-cavity spacing of 8 mm failed.