Fracture characteristics of Al-Si and Al-Fe system powder metallurgy alloys

Static and dynamic fracture toughness tests were carried out on Al-18 mass%Si and Al-8 mass%Fe powder metallurgy(P/M) alloys. The fracture mechanisms of the P/M alloys were investigated which was related to the microstructure. Both static and dynamic fracture toughness are greater in the Al-Si alloy than in the Al-Fe alloy. Crack propagates in the matrix or along the interface between matrix and particles according to the size of the particles under both static anddynamic conditions. Crack path which acrosses the coarse Si particles is also observed in the Al-Si alloy. The characteristic distance, l^*₀, which dominates the fracture initiation is round from two through four times of the interparticlespacing of coarse particles under static conditions while that is equivalent to the distance between the fatigueprecrack and the nearest coarse particle under dynamic conditions.