Producing Al-Zn Alloy Coating on the Pure Al Substrate by Solid-State Friction Surfa ce Alloying

Abstract

Using friction-assisted solid-state processes in the surface engineering of metals and alloys addresses the challenges involved in liquid-state methods. In the present work, friction surface alloying (FSA) was used to deposit Al-Zn alloy coating as a layer on pure Al substrate. Zn powder was filled in the holes produced longitudinally in a pure Al rod and was used as the consumable rod. Processing was done at 1100 rpm with 25 mm/min feed rate at a worktable vertical feed of 5 mm/min. Due to the generated heat during the friction surfacing, the zinc reinforcement was melted and a solid solution alloy of Al-Zn was produced on pure Al. The cross-sectional microstructure clearly indicated a strong metallurgical bonding at the alloy-substrate interface. Phase analysis carried out by X-ray diffraction studies confirms the developed Al-Zn alloy in the coated surface. Hardness measurements at the cross-section and at the surface demonstrated improvement (75.2±8.3 HV0.1) compared with the substrate (36.5±7.1 HV0.1) due to the formation of the alloy. Corrosion experiments by polarization studies revealed significant improvement in the corrosion resistance for the produced surface alloy as reflected from the lower corrosion current density (1.39×10–4 A/cm2) compared with the substrate (1.83×10–3 A/cm2). Higher tensile strength (245.5±5.2 MPa) was measured for the developed alloy than the substrate (182.1±6.9 MPa) without losing the ductility significantly. The results demonstrate the potential of FSA to develop surface alloys within the solid-state itself.