Investigation of the microstructure, electrical and mechanical properties of Al-CNTs-B₄C composite prepared by double-step stir casting for power transmission conductor

Monolithic aluminium alloy is amodern engineeringmaterial that is in high demand owing to its excellent performance and versatility. It has a high electrical conductivity, lowdensity, high strength- to- weight ratio, and high resistance to corrosion.However, it lacks adequate resistance to creep, fatigue, stable microstructure, and strength at elevated temperatures.To overcome these deficiencies, aluminium matrix composites are developed.Thiswork focuses on an experimental investigation of the microstructure, mechanical strength, and electrical conductivity of Al-CNTs-B4Ccomposite consolidated by a double-step stir casting technique.An x-ray diffractometer, transmission electronmicroscopy, and afield-emission scanning electronmicroscope fitted with energy dispersive x-ray spectroscopy were used to characterize the start-up powders and the cast samples.ABrinell tester was used tomeasure themicrohardness of the cast samples.Afour-point probe meterwas used to determine the electrical conductivity.The microstructural results revealed formation of Al4C3 andAl3BCintermetallics, B4Cphase and amorphous carbon precipitate.Marginally improved electrical conductivity of 33.33×107Sm-1 (65.1% IACS) was obtained with Al-5CNTs-15B4C, together with high microhardness of 725.72MPa.The microhardness improved by 94.7% overmonolithic pure Al.The double-step stir casting enhanced the homogenous dispersion of the reinforcements. The improvements in themechanical properties and electrical conductivity were attributed to the synergy between B4Cand CNTswhich induced Orowan looping, load transfer effect, plastic deformation and dislocation pinning in the composite. It is recommended that this compositewill perform creditably in power transmission.