THE ROLE OF 2 NANOLAYER IN FORMATION OF THE CARBON REINFORCEMENT-AZ91E MAGNESIUM ALLOY INTERFACE MICROSTRUCTURE
Anita Olszówka-Myalska, Agnieszka Botor-Probierz
Quarterly No. 4, 2010 pages 348-355
DOI:
keywords: composites, carbon fibers, glassy carbon particles, AZ91E magnesium alloy, SiO2 nanocoating, interface
abstract Results of microstructure investigations of two types of AZ91E magnesium alloy matrix composites reinforced with carbon fibers and glassy carbon particles were presented. The SiO2 nanocoating with thickness of 100 nm deposited by the sol-gel method was used for the surface modification of both fibers and particles. The having an amorphous structure uniformly covers surface of both carbon fibers and glassy carbon particles of irregular shape. Composite samples were obtained in vacuum of 2.5 Pa in Degussa press. The infiltration process at the temperature of 670°C associated with pressing was used in case of carbon fibers consolidation as well as in case of pressing of glassy carbon particles-AZ91E powder mixture at the temperature of 650°C. Composite microstructure was analyzed by scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM - BF, HAADF, EDS, SADP). Parameters of consolidation processes used in the experiment ensured the uniform reinforcement distribution. During microstructure investigations the main attention was focused at the carbon reinforcement/SiO2 nanocoating/magnesium alloy interface. The oxide layer was detected in the interface but it was not the SiO2. The oxide layer contained mainly Al and Mg and traces of Si and Zn. The dispersed precipitations of the Al12Mg17 phase dopped with Zn were identified around the carbon fibers. Results of experiment showed that during consolidation process with liquid phase the structure of SiO2 nanocoating was subject to transformation according to the presented model. It means that the SiO2 coating plays the role of the active diffusion barrier for the carbon-AZ91E alloy system.