Effect of strain rate on low-cycle fatigue behaviour and mechanism of SiCp/Ly12 composite

A study has been made of the behaviour and fracture mechanism of SiCp/Ly12 composite in low-cycle impact fatigue (LCIF). The results showed that in LCIF in conditions of lower strain range-higher fatigue life, a cyclic stability: even cyclic softening, happened in the composite. In the LCIF test the fatigue life of the SiCp/Ly12 composite was sensitive to the content of SiC particles so the LCIF test is an almost unique method to distinguish small differences in ductility among these brittle materials. As the composite fractured first in the SiC particles a break, smash or interface separation occurred, then in the matrix a cavities coalescence fracture was induced. Finally it is seen that under many circumstances the SIC particles were really a weakening phase while increasing the rigidity of the composite, therefore when the composite is used as a structural material great attention must be paid to its behavior. (C) 1997 Elsevier Science S.A.