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

The effects of solid solution treatment on microstructure and mechanical properties of SiCp/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 SiCp to eutectic dissolution and grain coarsening. Interestingly, interface reactions of SiCp/2024Al, similar to those during fabrication, continuously occur during the solution treatment. Simultaneously, two constituents of the interface reaction layer, Al2Cu and MgAl2O4 phases, change from the original agglomerated distribution to uniform distribution and finally to segregated form again accompanied by coarsening and phase transformation of Al2Cu into Al2CuMg. Such changes of the reaction layer significantly affect the interface debonding of SiCp/matrix or SiCp 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.

Automated summary

The solid solution treatment process of SiCp/2024 Al matrix composite has a hysteresis effect due to the SiCp particles, and the morphological changes of interface reaction layers during the treatment significantly affect the mechanical properties of the composite.