Ajay Sidpara

Stir casting is a cost‐effective and economical technique for producing aluminum matrix composites (AMCs). However, it is necessary to address the issue of poor wettability and lower interfacial interaction between nanoreinforcing particles and the matrix. Ultrasonically aided solidification is an effective solution to these issues. In the present study, an Al6061/graphene nanoplatelet (GNP) nanocomposite is manufactured using the ultrasonic‐assisted stir casting (USASC) technique. Magnesium (Mg) is added as a wetting agent to reduce clustering and improve the homogeneous dispersion of GNPs in the matrix. A detailed examination of the mechanical and microstructural properties of AMCs synthesized with bottom pouring stir casting (BPSC) and USASC techniques is investigated and compared. The USASC nanocomposite demonstrates better dispersion of the GNP particles and a ≈92% reduction in porosity attributed to enhanced wettability and cavitation effect compared to the BPSC‐based nanocomposite. The USASC‐based nanocomposite shows ≈106, ≈494%, and ≈347% improvement in nanohardness, ultimate tensile strength, and yield strength, respectively, compared to the BPSC nanocomposite. The scanning electron microscope fractograph of the USASC‐based nanocomposite reveals a mixed kind of brittle–ductile failure mechanism. Theoretical calculations of yield strength indicate that the load transfer, followed by coefficient of thermal expansion mismatch, significantly contributes to the strengthening of the nanocomposite compared to other mechanisms.

Magnetorheological finishing (MRF) is used to precisely finish various materials such as hard crystals, optical, and brittle materials. In this article, the thermal behavior of MRF process is studied theoretically and experimentally on thin copper substrate surface by varying rotational speed and working gap. The wall shear stress (WSS) represents the frictional force per unit area exerted by the flowing MR fluid on the workpiece surface and it is determined using three-dimensional (3D) computational fluid dynamics (CFD) numerical simulations that use a dynamic viscosity model based on the variable magnetic flux density (MFD). A thermal model is proposed to predict heat generation and temperature rise on the workpiece surface with the help of energy partitioning, heat conduction equations, and WSS. It is observed that the temperature rises with increasing the rotational speed and reducing the working gap. Considering MR fluid with only abrasive particles, the theoretical temperature rise of 21.32 °C was predicted. While MR fluid with carbonyl iron particles (CIPs) and abrasive particles, the theoretical temperature rise was 19.37 °C. In experiments, the maximum temperature rise of 14.8 °C was obtained. Finite element analysis is performed to estimate magnetic flux density variation on the workpiece surface and viscosity variation over the workpiece surface. Surface roughness (S_a) reduced from an initial value of 0.236 μm to 0.079 μm at 600 RPM tool rotational speed and 3.0 mm working gap.