In situ microfracture observation of Cu-based amorphous alloy matrix composites containing copper or brass particles

This study aims at investigating fracture mechanisms occurring in Cu-based amorphous alloy matrix composites containing ductile Cu or brass particles. Amorphous alloy powders were mixed with 20-40 vol.% of Cu or brass powders, and were consolidated at 460 °C for 1/2 min under 700 MPa by spark plasma sintering (SPS) equipment. The consolidated composites contained Cu or brass particles homogeneously distributed in the amorphous matrix, and showed a considerable plastic strain under a compressive loading condition, whereas their strength was lower than that of the monolithic amorphous alloy. Microfracture mechanisms were investigated by directly observing microfracture processes using an in situ loading stage. Cu or brass particles present in the composites acted as blocking sites of the propagation of cracks initiated at the amorphous matrix, and provided the stable crack growth. In front of some Cu or brass particles, the crack blunting, deflecting, and bridging were also observed, and the final crack propagation path showed frequent stops of cracks. These findings suggested that the composites consolidated by the SPS presented new possibilities of application to structural materials or parts satisfying excellent mechanical properties and large size requirements.