The effect of cold and hot pressing on mechanical properties and tribological behavior of Mg-Al2O3nanocomposites

In this research, pure powder of Mg was mixed with 0, 1.5, 3, 5%vol. of Aluminium oxide in a planetary mill. Next, the powder mixture was poured in a mold and pressed in two diverse conditions of (1) hot pressing at 600 MPa pressure and 450 degrees C temperature for 25 min and (2) cold pressing at 600 MPa pressure in the room temperature and samples sintered in a furnace under Argon gas at 450 degrees C temperature for 2 h. Density and mechanical properties, e.g., microhardness, and wear properties of the produced samples were assessed. Also, metallographic photography and SEM analysis were done on the samples to investigate their microstructure properties and analyze their worn surfaces. The results revealed that with an increase in the volume of the reinforcement particles, the experimental density and microhardness soared, on the contrary, the relative density showed a decreasing trend. Moreover, the results of the microhardness analysis for the produced samples via hot pressing method were achieved better than those of cold pressing, as the highest hardness 81HV was achieved for %5 vol. Al(2)O(3)containing samples produced through the hot pressing method, which was about %18 more than that of the %5 vol. Al(2)O(3)containing samples produced via the cold pressing method and was about %85 more than of the pure Mg samples produced via the hot pressing method. The results of the samples' wear properties also signified the improvement of wear resistance and decrease of mass loss with an increase in the volume fraction of the reinforcement particles. The lowest mass loss of 2.5 g was obtained for the sample containing %5 vol. of the reinforcement particle which was produced via the hot pressing method. This value was less about %40 and %80 compared to pure Mg samples produced via hot and cold pressing methods, respectively.