EVALUATION OF HOT HARDNESS, CREEP, COEFFICIENT OF THERMAL EXPANSION AND HIGH TEMPERATURE MICROSTRUCTURE OF 6061 Al-SiC_p COMPOSITES

摘要

The hardness of 6061 Al-10percent SiC_p and Al-25wtpercent SiC_p were measured from room temperature to 823 K using a hot hardness tester. The hardness versus temperature data can be represented by plotting modulus compensated hardness (H/E) versus homologous temperature (T/T_m) It is noted that up to 0.6 T_m the fall in hardness is less and creep is insignificant. Indentation creep of the composite was determined in the temperature range of 623 K to 673 K. The stress exponents of 6061 Al-10percent SiC_p and 6061 Al-250. SiC_p were 7 and 10.1 respectively. The activation energy obtained was 176+-4 kJ.mol~(-1) and 272+-6 kJ.mol~(-1) respectively for these composites. The expansion behaviour of the above mentioned composite has been determined up to 823 K. High temperature microscopy was carried out for evaluating the microstructure and the particle/matrix interface behaviour. It is noted that the cavitation and decohesion of the particle occurs in the temperature range of 773 to 858K.