Experimental and optimization studies of friction stir processed Cu-TiB2 surface composites

The present study aims to fabricate different Copper surface composites (Cu-SCs) such as Copper-Silicon Carbide (Cu-SiC), Copper-Boron Carbide (Cu-B4C), Copper-Titanium Diboride (Cu-TiB2) with enhanced mechanical properties using friction stir processing. The Cu-SCs were fabricated at different levels of tool rotational speed (TRS), traverse speed (TS), and Vol. % of micro-sized Boron Carbide (B4C), Silicon Carbide (SiC), and Titanium Diboride (TiB2) reinforcements using blind hole method. The mechanical characteristics such as ultimate tensile strength (UTS), yield strength (YS), percentage of elongation (%EL), impact toughness (IT), and microhardness (H) of the Cu-SCs were evaluated and analyzed. In the next stage, the process parameters were optimized using a graph theory algorithm and utility concept and the TRS, and TS were 1120 rev/min, and 40 mm/min respectively. The Cu-SCs fabricated by using taper threaded cylindrical tool pin profile at four Vol.% of TiB2 possess enhanced the mechanical characteristics such as UTS, YS, % EL, IT, and H up to 282.07 MPa, 197.76 MPa, 12.96%, 16.67 J, and 168.6 HV. This was happened due to the increased recrystallization temperature, the pining effect, and restricting the grain boundary sliding. The microstructure in the stir zone of Cu-SCs fabricated with 4 Vol. % of SiC, 4 Vol. % of B4C, and 4 Vol. % of TiB2 particles exhibit fine grains. This is attributed to uniform distribution of the particles in the copper surface composites. The mechanical characteristics were also correlated with microstructures and fracture features.