Effect of graphene and process parameters on mechanical performance and electrical resistance of aluminum to copper friction stir joint

Effects of graphene, tool rotational speed and pass number were studied on the reliability and electrical resistance of the aluminum to copper friction stir welds. Addition of graphene was an effective solution to overcome the increase in the electrical resistance of the aluminum/copper joints. Indeed, presence of graphene decreased the electrical resistance of the joints to the values comparable with that of the copper base metal. However, joint tensile strength was not affected significantly by graphene. Decrease in the tool rotational speed improved the dispersion of the graphene particles and tensile strength, while reduced the electrical resistance. Tensile strength of the joint reached up to ∼80% of the aluminum base metal strength at the optimum condition. Decreasing effect of the appropriate distribution of the graphene particles on the joint electrical resistance dominated the increasing effect of the Al/Cu intermetallic compounds (i.e. Al₂Cu and Al₄Cu₉ phases) formed in the joint zone. (paper)