Study fatigue crack initiation in TiB_2/Al-Cu-Mg composite by in-situ SEM and X-ray microtomography

摘要

In this work, the fatigue initiation in a particle-reinforced aluminium matrix composite was investigated. The fatigue cracks mostly initiate at multiple sites associated with TiB_2 and second phases (S/θ). Only few cracks initiate from individual TiB_2, and they are caused by matrix fracture close to the high density dislocation zones around TiB_2. Furthermore, the growth capability of initiated cracks is dependent on their stress intensity factors at crack tip. Only crack initated from largest-sized (S/θ + TiB_2) cluster is developed into main crack. During main crack evolution, the small crack grows along slip traces and retarded by grain boundaries and/or TiB_2.