Research Article Optimization of Stir Casting Variables for Production of Multiwalled Carbon Nanotubes: AA7149 Composite Mohamad Reda A. Refaai, 1 Samraj Ravi, 2 S. Prasath , 3 Maridurai Thirupathy, 4 Ram Subbiah, 5 and Abdi Diriba 3 1 Department of Mechanical Engineering, College of Engineering, Prince Sattam Bin Abdulaziz University, Saudi Arabia Alkharj 16273 2 Department of Mechanical Engineering, Chennai Institute of Technology, Chennai, Tamil Nadu, India 3 Department of Mechanical Engineering, Mizan Tepi University, Ethiopia 4 Department of Mechanical Engineering, Saveetha School of Engineering, SIMATS, Chennai, Tamil Nadu, India 5 Department of Mechanical Engineering, Gokaraju Rangaraju Institute of Engineering and Technology, Hyderabad, 500090 Telangana, India Correspondence should be addressed to Abdi Diriba; abdi@mtu.edu.et Received 17 February 2022; Accepted 16 April 2022; Published 23 June 2022 Academic Editor: Hiwa M. Ahmed Copyright © 2022 Mohamad Reda A. Refaai et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Combining liquefied metals with multiwalled carbon nanotube-aluminium alloy 7149 composites enables the creation of intricate designs and mass production was manufactured using mechanical stir casting, thixoforming, and T6 heat treatment. Taguchi with two factorial levels was chosen to investigate the optimum parameter and affect variables such as carbon nanotube concentration, magnesium wettability, and ring mechanical stir duration were used in addition to a robust design of experiments. The response variables were the S/N ratio, hardness, and ultimate tensile strength. The fourth DOE run resulted in an optimised nanocomposite with 107.8 HV hardness and 278.1 MPa tensile strength that contained 0.75 wt.% magnesium and 1% multiwalled carbon nanotube and stirred time of 10 minutes. The as-forged AA7149 alloy had a lower hardness value (76.3%) but a higher ultimate tensile strength value (108.4%). It was demonstrated that combining thixoforming and heat treatment improves the mechanical properties of multiwalled carbon nanotube produced under mechanical stir casting conditions. 1. Introduction Multiwalled carbon nanotubes have been employed in a num- ber of investigations on composites. Load transmission, strengthening, and thermal expansion strengthening are just a few of the factors that go into making multiwalled carbon nanotubes so strong [1, 2]. The key obstacles in metal matrix composites manufacture are often achieving homogeneous distribution and adequate wetting qualities, as well as interfa- cial phases between reinforced particles and matrix [3]. Rather than relying on more traditional approaches, the powder met- allurgy industry has opted to tackle these problems instead. Processing powder metallurgy, on the other hand, is prohibi- tively expensive and can only be used for simple, not elaborate, parts [4, 5]. It is possible to use liquid metallurgy processing, a cheaper option [6], for complex designs and large-scale manufacturing. It is, however, difficult to overcome the large density difference between multiwalled carbon nanotube and aluminium alloy. Composite reinforcement requires consider- ation of a variety of factors, including the purification and acti- vation of reinforced materials, the mixing of those materials, the amount of wetting agent, and other variables (sintering, extrusion, compaction, thixoforming, and heat treatment). Taguchi is a great technique for optimising parameters for composite development conferring to [7, 8] have shown that a number of variables, including the quantity of strengthened material, processing temperatures, wettability agents, and stirring method, have an effect on the physical Hindawi Journal of Nanomaterials Volume 2022, Article ID 2535470, 7 pages https://doi.org/10.1155/2022/2535470