Bending Properties and Failure Mechanism of Continuous W-Core-SiC Fiber-Reinforced 2024 and 6061 Aluminum Matrix Composites

Abstract

In order to investigate the effect of different matrices on the bending properties and fracture behavior of the continuous W-core-SiC fiber-reinforced aluminum matrix (SiCf/Al) composites, 30 vol.% SiCf/2024Al and 30 vol.% SiCf/6061Al composites were prepared via matrix coating and hot isostatic pressing. Samples from these composites were subjected to the push-out test and three-point bending test with in situ SEM. The microstructure of the SiCf/Al composites was examined by SEM and TEM. Results showed that there were coarse AlCuFeMn and Al2Cu phases in the matrix of the SiCf/2024Al composite, and needle-like Al4C3 phase at the interface between fiber and matrix. For the SiCf/6061Al composite, there were no coarse second phase in the matrix and no Al4C3 phase at the interface between fiber and matrix. The interfacial shear strength of the SiCf/2024Al composite (~ 37 MPa) was relatively larger than that of the SiCf/6061Al composite (~ 34 MPa), indicating a relatively strong interface bonding for the SiCf/2024Al composite. The bending strength of the SiCf/6061Al composite (1091 MPa) was superior to that of the SiCf/2024Al composite (968 MPa). For 30 vol.% SiCf/2024Al composite, cracks were initiated at the edge of the coarse second phase under bending load and propagated along the grain boundary of matrix. The crack passed directly through SiC fibers due to the strong interface bonding and needle-like Al4C3 phases formed by interfacial reaction, and the propagation rate was fast. For 30 vol.% SiCf/6061Al composite, the crack was initiated at the interface between fiber and matrix when the plastic deformation of matrix was retarded at the first SiC fiber. Then, the crack passed around SiC fibers and propagated in forms of crack bridging and deflection due to the suitable interface bonding, and the propagation rate was slow.