Synthesis of nickel coated graphene and analysis of the efficacy of its reinforcement on the hyper eutectic AlSi alloys that are grain modified and refined

Abstract

Investigation on the impact of grain refiners and modifiers on the mechanical characteristics of Aluminium Silicon alloys is an ongoing subject. It is understood that the mechanical properties of AlSi alloys can be significantly improved by refining and modifying the grains and by adding the solid lubricants. In the present work, synthesis of nickel coated graphene particles is carried out. The die cast hyper eutectic AlSi alloys are subjected to grain refinement and modification with simultaneous reinforcement of nickel coated graphene powder. Nickel coated graphene particles are synthesised by electroless plating. After graphene is pre-treated, electroless plating was conducted in a bath having nickel nitrate as source of nickel along with sodium borohydrate as a reducing agent. During this procedure, ultrasonic agitation was used to improvise the coating properties. The coated graphene powder was characterised by EDAX which revealed the Ni coating on the surface of graphene. AlSi alloys of three distinct compositions are synthesised using die casting method. The first alloy comprises of aluminium silicon as the base alloy. The second alloy comprises of the nickel coated graphene reinforced aluminium silicon alloy. The third alloy comprises of aluminium silicon alloy which is grain refined, modified and further reinforced with the nickel coated graphene powder. The three different compositions of AlSi alloys thus casted, are tested for the mechanical properties like tensile strength and Vicker's hardness test. They are also tested for the microstructure by scanning electron microscopy and optical microstructure. The tensile strength and hardness are the highest for that alloy that is simultaneously grain refined, modified and nickel coated graphene reinforced. The microstructure of the third alloy displayed a clear transition of the plate like silicon to globular shaped eutectic silicon with uniformly distributed graphene. • Synthesis of Nickel coated Graphene powder (NCG). • Examine the coating of Nickel on the Graphene. • Preparation of the metal composites by die casting the Aluminium Silicon alloys. • Study the properties of alloys prepared using grain refiners, modifiers and NCG. • Report the tensile, micro hardness values and microstructure of the casted alloys.