J. Mater. Sci. Technol. ›› 2018, Vol. 34 ›› Issue (9): 1580-1591.DOI: 10.1016/j.jmst.2018.03.004

• Orginal Article • Previous Articles     Next Articles

Microstructure and mechanical properties of hot extruded 6016 aluminum alloy/graphite composites

Mohamed M. El-Sayed Selemanab*(), Mohamed M.Z. Ahmedabc, Sabbah Atayaabd   

  1. a Department of Metallurgical and Materials Engineering, Faculty of Petroleum and Mining Engineering, Suez University, 43518 Suez, Egypt
    b Suez and Sinai Metallurgical and Materials Research Center of Scientific Excellence (SSMMR-CSE), 43518, Suez, Egypt
    c The British University in Egypt, Mechanical Engineering Department, El-Sherouk City, 11837, Cairo, Egypt
    d Department of Mechanical Engineering, College of Engineering, Al Imam Mohammad Ibn Saud Islamic University, Riyadh 11432, Saudi Arabia
  • Received:2018-01-19 Revised:2018-02-21 Accepted:2018-03-05 Online:2018-09-20 Published:2018-09-25
  • Contact: M. El-Sayed Seleman Mohamed

Abstract:

The incorporation of graphite particles into AA6016 aluminum alloy matrix to fabricate metal/ceramic composites is still a great challenge and various parameters should be considered. In this study, dense AA6016 aluminum alloy/(0-20 wt%) graphite composites have successfully been fabricated by powder metallurgy process. At first, the mixed aluminum and graphite powders were cold compacted at 200 MPa and then sintered at 500 °C for 1 h followed by hot extrusion at 450 °C. The influence of ceramic phases (free graphite and in-situ formed carbides) on microstructure, physical and mechanical properties of the produced composites were finally investigated. The results show that the fabricated composites have a relative density of over 98%. SEM observations indicate that the graphite has a good dispersion in the alloy matrix even at high graphite content. Hardness of all the produced composites was higher than that of aluminum alloy matrix. No cracks were observed at strain less than 23% for all hot extruded materials. Compressive strength, reduction in height, ultimate tensile stress, fracture stress, yield stress, and fracture strain of all Al/graphite composites were determined by high precision second order equations. Both compressive and ultimate tensile strengths have been correlated to microstructure constituents with focusing on the in-situ formed ceramic phases, silicon carbide (SiC) and aluminum carbide (Al4C3). The ductile fracture mode of the produced composites became less dominant with increasing free graphite content and in-situ formed carbides. Wear resistance of Al/graphite composites was increased with increasing graphite content. Aluminum/20 wt% graphite composite exhibited superior wear resistance over that of AA6016 aluminum alloy.

Key words: AA6016/graphite composites, Hot extrusion, In-situ carbides, Mechanical properties, Wear resistance, Fracture behavior