Effects of solid solution treatment on microstructure and mechanical properties of SiC_p/2024 Al composite: A comparison with 2024 Al alloy

摘要

The effects of solid solution treatment on microstructure and mechanical properties of SiC_p/2024 Al matrix composite fabricated via powder thixoforming were investigated, as well as those of 2024 matrix alloy for comparison. The results indicate that the solution progress of the composite is more hysteretic than that of the alloy due to the obstacle role of SiC_p to eutectic dissolution and grain coarsening. Interestingly, interface reactions of SiC_p/2024Al, similar to those during fabrication, continuously occur during the solution treatment. Simultaneously, two constituents of the interface reaction layer, Al_2Cu and MgAl_2O_4 phases, change from the original agglomerated distribution to uniform distribution and finally to segregated form again accompanied by coarsening and phase transformation of Al_2Cu into Al_2CuMg. Such changes of the reaction layer significantly affect the interface debonding of SiC_p/matrix or SiC_p cracking during tensile test, and thus, the fracture regime and mechanical properties of the composite. The achieved modified shear-lag strengthening model by considering the strengthening effect of eutectic compounds can well interpret the strengthening mechanisms of these two materials, especially the variations of each strengthening mechanism contribution with solution time and the corresponding differences between these two materials.