Microstructure and mechanical properties of non-stoichiometric MgAl2O4-spinel bodies

This work studies the cold mechanical and tribological properties of dense non-stoichiometric MgAl2O4-spinel ceramics, processed by single firing up t o 1700 degrees C, from commercial Chinese dead-burned magnesite/calcined ba uxite batches. The mechanical properties were determined by means of plasti c hardness and Young's modulus, whereas wear and friction resistance method s were applied to followup the tribological properties. The results of thes e tests are interpreted in relation to phase composition and microstructure of the dense spinel ceramics. it is concluded that dense MgO- and Al2O3-ri ch ceramics with greater than or equal to 90 % relative density and compose d mainly of a direct-bonded spinel solid solution network with less than or equal to 12,0 % Ca- and Mg-silicate phases could be obtained. Both ceramic s show plastic hardness of 21,6...22,6 CPa and Young's modulus of 286...295 CPa which are comparable with the corresponding values of pure MgAl2O4-spi nel. MgO-rich spinel ceramics have much higher wear resistance than Al2O3-r ich ceramics, when the wearing load increases from 20 up to 40N.