Mechanical and Microstructural Properties of [B.sub.4]C/W Reinforced Copper Matrix Composite Using a Friction Stir-Welding Process

Copper metal matrix composites (CMC) are broadly employed in various applications in the fields of space, aviation, automobile and electronics industries. The welding of CMC in using conventional methods is very difficult and expensive due to its crystallographic nature. Friction stir welding (FSW) is a more prominent and reliable technique for welding than conventional methods. Therefore, this work is based on work with CMC material, which is prepared with a stir-casting technique. Pure copper (Cu) is reinforced with tungsten (W) and boron carbide ([B.sub.4]C) particles in different combinations and welded using the FSW process to study the mechanical and micro-structural properties. Multiobjective decision-making methods, such as the technique for order preference by similarity to ideal solution (TOPSIS) and grey relational analysis (GRA) are used to find optimal parameter combination. The experiments are planned according to the L 18 orthogonal array (OA) using the most influential parameters, such as reinforcement the percentage of [B.sub.4]C, tool rotational speed, welding speed, and axial force. The performance of outcomes is measured based on the responses such as tensile strength, hardness, and impact strength of the weld joint. Based on the results 15 % of [B.sub.4]C reinforcement, 900 RPM rotational speed, 15 mm/min welding speed and 6 kN axial forces are optimal for better mechanical strength in the welding with TOPSIS and GRA techniques. Additionally, scanning electron microscopic image (SEM) analyses were carried out for better understanding of weldments' microstructure changes. Keywords: friction stir welding, copper, metal matrix composite, boron carbide