Electrochemical corrosion and tribological behaviour of AA6063/Si3N4/Cu(NO3)2 composite processed using single-pass ECAPA route with 120° die angle

Abstract

We studied the electrochemical corrosion of AA6063 aluminium composite fabricated using the stir casting technique and processed using Equal-Channel Angular Pressing (ECAP). Potentiodynamic polarisation and Electrochemical Impedance Spectroscopy were used to assess the corrosion resistance of a metal and ceramic mixture reinforced aluminium composite under various processing conditions. The corrosion resistance of the fabricated composite increased with addition of the metallic reinforcement. The AA6063/(12%)Si3N4/(6%)Cu(NO3)2 composite exhibited a 63% lower corrosion rate. Increased dislocation density, grain processing, participate re-distribution, alteration of the cathodic site surface, and an increase in the number of grain boundaries changed the corrosion behaviour after ECAPA. Elongated grains and grain boundaries are more susceptible to combative solutions, resulting in corrosion at these locations owing to lower corrosion resistance than cast specimens. However, after ECAP, the specimen exhibits a shallow and uniformly corroded surface. Subsequently, a Pin-on-Disc tribometer was used for the dry sliding tribological characterisation of the nitride and nitrate particle reinforced AA6063/Si3N4/Cu(NO3)2 hybrid metal matrix composite according to the ASTM G99-05 standards using L27 orthogonal array. The ECAPA with the process parameters of 10 N applied load, 1000 m sliding distance, and 400 rpm sliding speed yielded 73% higher wear resistance for the above composite compared to the cast composite, along with a 40.7% reduction in the coefficient of friction.

Keywords

• Metallic composites
• Corrosion
• Grain boundaries
• ECAP
• Metallic reinforcement
• Deformation and dislocation