Fabrication of Al matrix composite reinforced with Fe-Cu particles using friction stir processing

Abstract

Friction stir processing (FSP), as an advanced technique, was employed to fabricate in situ aluminum composites with the aim to elucidate the correlation between microstructure and mechanical properties of the obtained composites. The novelty of the work is to utilize simultaneous incorporation of Fe and Cu powders into the friction stir zone in order to fabricate in situ aluminum composites. To achieve the goal, the loading content of Cu and Fe powders and the process pass number (1 pass to 5 passes) were altered. While the total loading content of Fe and Cu powders was kept constant, the weight percentages of these reinforcements were varied (25%, 50%, and 75%). Microstructural characteristics were examined using scanning electron microscopy and optical microscopy. Five passes FSP resulted in smaller grain sizes of the Al matrix, smaller and less agglomeration of the reinforcements as well as homogeneous dispersion of the reinforcement features and thus, enhancement of the mechanical properties of the composites. X-ray analysis and energy dispersive spectroscopy confirmed in situ formation of Fe-Al and Al-Cu intermetallic compounds in the composites. The tensile testing outcomes proposed the 50wt% Fe-50wt% Cu/Al composite fabricated in 5 passes as the optimum formulation achieved in this research. This can be attributed to the smaller grain size of the matrix in the friction stirred zone and more homogeneous dispersion of the reinforcements in the matrix. Furthermore, this strengthening was affected from the presence of more amounts of well dispersed intermetallic compounds in situ formed during 5 passes. The average tensile strength (207 MPa) and hardness (73 Vickers) of the composite were approximately 175% and 160% greater than that of the unreinforced aluminum (75 MPa, 28 Vickers), respectively. Increasing the process pass number from 3 to 5 passes not only had strengthening and hardening effects but also improved the composite elongation at break.