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

The hardness of 6061 Al-10wt% SiCp and Al-25wt% SiCp were measured fro m room temperature to 823 K using a hot hardness tester. The hardness versus temperature data can be represented by plotting modulus compens ated 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 insigni ficant. Indentation creep of the composite was detemlined in the tempe rature range of 623 K to 673 K. The stress exponents of 6061 Al-10% Si Cp and 6061 Al-25% SiCp were 7 and 10.1 respectively. The activation e nergy obtained was 176+/-4 kJ.mol(-1) and 272+/-6 kJ.mol(-1) respectiv ely for these composites. The expansion behaviour of the above mention ed composite has been determined up to 823 K. High temperature microsc opy was carried out for evaluating the microstructure and the particle /matrix interface behaviour It is noted that the cavitation and decohe sion of the particle occurs in the temperature range of 773 to 858 K.