Surface reinforcement of AA5083-H111 by friction stir processing assisted by electrical current

• Application of external heat source in FSP to surface reinforcement with alumina.
• Characterization of current density distribution by numerical modelling.
• Reinforced depth increased by 500% compared to conventional FSP.
• Alumina particles were homogeneously distributed.
• Hardness profile was smooth which is better for wear applications.
• Electrical current did not affect base material surface hardness.

This paper presents a variant of friction stir processing (FSP) assisted by electric current for the production of surface composites in aluminium, reinforced with alumina particles. The main objective was to improve the overall material surface reinforcing process by using this variant. Numerical simulations were performed to study the electrical current density and flow patterns in the FSP tool, and in the processed zone. The FSP tool was adapted to the specificities of the application. The concept was experimentally validated by pre-placing alumina particles with median sizes of 45 μm, over AA5083-H111 plates and friction stir process these. Tests were performed with and without an electrical current of about 500 A for comparison purposes. The pre-deposition of alumina produced an increase in surface hardness of around 40%. Using this electrical current variant, a higher extension and depth of reinforced layer were observed, with an increase of about 500% and 40% in depth and in width, respectively, while the surface substrate hardness dropped by 10%. The particles were more uniformly distributed and sparser.

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