Mechanical properties study of particles reinforced aluminum matrix composites by micro-indentation experiments

By using instrumental micro-indentation technique, the microhardness and Young＇s modulus of SiC particles reinforced aluminum matrix composites were investigated with micro- compression-tester （MCT）. The micro-indentation experiments were performed with different max- imum loads, and with three loading speeds of 2.231, 4.462 and 19.368 mN/s respectively. During the investigation, matrix, particle and interface were tested by micro-indentation experiments. The results exhibit that the variations of Young＇s modulus and microhardness at particle, matrix and interface were highly dependent on the loading conditions （maximum load and loading speed） and the locations of indentation. Micro-indentation hardness experiments of matrix show the indentation size effects, i.e. the indentation hardness decreased with the indentation depth increas- ing. During the analysis, the effect of loading conditions on Young＇s modulus and microhardness were explained. Besides, the elastic-plastic properties of matrix were analyzed. The validity of cal- culated results was identified by finite element simulation. And the simulation results had been pre- liminarily analyzed from statistical aspect.

Wear Behavior of Cold Pressed and Sintered Al_2O_3/TiC/CaF_2-Al_2O_3/TiC Laminated Ceramic Composite

A novel laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite was fabricated through cold pressing and sintering to achieve better anti-wear performance, such as low friction coefficient and low wear rate. Al2O3/TiC/CaF2 and Al2O3/TiC composites were alternatively built layer-by-layer to obtain a sandwich structure. Solid lubricant CaF2 was added evenly into the Al2O3/TiC/CaF2 layer to reduce the friction and wear. Al2O3/TiC ceramic was also cold pressed and sintered for comparison. Friction analysis of the two ceramics was then conducted via a wear-and-tear machine. Worn surface and surface compositions were examined by scanning electron microscopy and energy dispersion spectrum, respectively. Results showed that the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite has lower friction coefficient and lower wear rate than those of Al2O3/TiC ceramic alone because of the addition of CaF2 into the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite. Under the friction load, the tiny CaF2 particles were scraped from the Al2O3/TiC/CaF2 layer and spread on friction pairs before falling off into micropits. This process formed a smooth, self-lubricating film, which led to better anti-wear properties. Adhesive wear is the main wear mechanism of Al2O3/TiC/CaF2 layer and abrasive wear is the main wear mechanism of Al2O3/TiC layer.