Development of Aluminium Metal Foams via Friction Stir Processing by Utilizing MgCO3 Precursor

Aluminium foams possess multi-functional properties and a low specific weight, making them one of the most suitable choices in the application domain of the automobile and aviation sectors, vibrating machining, and structural parts. Compared to traditional fabrication routes, friction stir processing (FSP) is gaining acceptance as it is a cost-effective, highly efficient, and innocuous process to fabricate the foam precursors from the bulk substrate. In the current study, FSP was utilized to develop a precursor with MgCO3 powder acting as the blowing agent. The FSP experiments were performed as per Taguchi’s L8 orthogonal array. The precursor was heat treated in an electric furnace at a holding temperature of 650 °C for 10 min. After the post-heat treatments, this precursor resulted in a porous structure due to the evolution of CO2 gas from the composite. The simultaneous effect of tool rotation speed, traverse speed, and shoulder diameter was investigated on the pore size and porosity of the foam produced. The composite parameter “unit stirring” is found to be closely related to the processed zone (PZ) and volume processing rate of the processed zone, pore size, and the degree of porosity. The highest porosity of 16.67% was obtained with an average pore size of 10.5 µm. The largest pore size, 17.8 µm, was observed to be associated with a porosity of 14.40%. The analysis of the Kiviat plot revealed that the values of the PZ area and volume processing rate possess a polar symmetry with unit stirring. The pore size and pore density were both found to be symmetrically distributed about the unit stirring.