Study On The Effect Of Cu Element On The Interface And Corrosion Behavior Of SiC_p/Al Composites In The Chloride Ion Environment

The differences in the interface and corrosion behavior of SiCp/Al composites in the chloride ion environment after surface electroless copper plating on SiC particles and matrix alloying with copper were mainly studied in this article.X-ray diffraction, scanning electron microscope(SEM) and energy dispersive spechoscopy were employed to observe the morphology and analyze the structure of the related composites interface. Potentiodyamic polarization curve, EIS, electrochemical noise test and SEM were used to evaluate electrochemical properties and to observe the corrosion morphology in 3.5%NaCl solution of the composite materials.Great differences were found in SiCp/Al composites interface which were made by the same process after surface electroless copper plating on SiC particles and matrix alloying with copper, as well as corrosion behavior in the chloride ion environment. The surfaces of SiC particles were coated by a dense, continuous copper layer after electroless copper plating, the copper plating layer improves the wettability between SiC particles and aluminum matrix, as well as increases the strength of the interface bonding and reduces A14C3 from reaction. Besides, CuAl2 phases will be generated by complex reaction between the copper layer and Al(l) at high temperature, improving the wettability between sic particles and liquid aluminum, The interface of SiCp/Al composites made by copper coated SiC particles has few cracks, holes and other defects, the Al4C3 and Si phase is significantly reduced. In the chloride ion environment, the lower corrosion potential, smaller corrosion current density and higher pitting potential indicated that SiCp/Al composites made by copper coated SiC particles has larger corrosion tendency and smaller corrosion rate and higher pitting corrosion resistance.Cu delayed the forming time of the composites passivation film and improve its resistance on corrosion. SiCp/Al composites made by copper coated SiC particles were showed pitting corrosion as the main forms of corrosion, while SiCp/Al composites made by non-copper coated SiC particles performance for pitting corrosion at the first stage, later turned to uniform corrosion.The interface of SiCp/Al composites which were made by matrix alloying with copper is generally poor, the surface of the particles cracking seriously and more interface defects were found, but the interface quality of SiCp/Al composites made by 6% was obviously improved. With the content of copper matrix increased, the content of Al4C3 phase in SiCp/Al composites decreased, CuAl2 content was increased. In the chloride ion environment, SiCp/Al composites which were made by matrix alloying with copper has the lower corrosion potential, means larger corrosion tendency. The higher Cu content in the matrix, the lower corrosion potential and higher corrosion current density the related SiCp/Al composites possessed, that indicate larger corrosion tendency and faster corrosion rate. SiCp/Al composites made by pure aluminum matrix performance for pitting corrosion at the first stage, later turned to uniform corrosion, however, SiCp/Al composites made by matrix alloying with copper occurrence for pitting corrosion first, then pits generate along the grain boundary of CuAl2 phase and grow to intergranular corrosion, further more, the accumulation of a large number of corrosion products cause the surface of the composite materials cannot bear the corresponding pressure, exfoliation occurs.