Development of surface nano-composite based on Mg-Cu-O ternary system on AZ91C alloy by friction stir processing and study of its tribological behavior Mahdie Farghadani m.farghadani@ma.iut.ac.ir Date of submission: 2015/5/25 Department of Materials Engineering Isfahan University of Technology, Isfahan: 84156-83111, Iran Degree: M.Sc Language: Farsi Supervisors: F. Karimzadeh, Karimzadeh_f@cc.iut.ac.ir M.H. Enayati, Ena87@cc.iut.ac.ir In this study, surface nanocomposite based on Mg-Cu intermetallic compounds was fabricated on the AZ91C alloy by friction stir processing (FSP). Either Cu or CuO powder was placed in grooves produced on AZ91C surface. In order to fabricate composite with no defects, improve Cu and Mg reaction, achive uniform distribution of reinforcement, the samples were processed with 6 passes at a tool rotational speed of 1000 rpm and transverse speed of 40 mm/min. XRD analysis was used to investigate the formation of the intermetallics compounds. The results revealed that Mg 2 Cu compound was formed in case of FSP of AZ91C/Cu composite. Reaction of copper oxide with Mg in case of AZ91C/CuO composite led to the formation of MgO and MgCu 2 reinforcement particles in addition to the Mg 2 Cu phase. FSPed AZ91C/CuO samples was T6 heat treated. Hardness of heat treated AZ91C/CuO sample was about 165 Hv wich is much higher than that for base metal (62 Hv), FSPed AZ91C/CuO and AZ91C/Cu composites (128 Hv and 114Hv respectively). Comparison of tensile and wear results proved that AZ91C/CuO composite had the best mechanical and tribological behavior. After fabrication of AZ91C/CuO composite, the UTS (Ultimate tensile strength) increased from 112.4 Mpa for as-received AZ91C to about 330 Mpa for FSPed AZ91C/CuO sample. Wear surface observation revealed the occurrence of abrasion and delamination mechanism. The depth and width of worn grooves were smaller in case of AZ91C/CuO sample. Because of the microcracks formation in T6 heat treated AZ91C/CuO samples thus wear rate was much lower in this sample, delamination and wear rate increased in comparison to un heat treated samples. Keywords: Surface nanocomposite, Magnesium alloy, Friction stir processing, Intermetallic compounds, Mg-Cu system.
