Fatigue properties of Al2O3-particle-reinforced 6061 aluminium alloy in the high-cycle regime

The fatigue properties of Al2O3-particle-reinforced and unreinforced 6061-T6 aluminium alloys were investigated in the regime from 5 x 10(5) to 10(9) cycles to failure under constant-amplitude, fully reversed loading conditions (R=-1) using smooth specimens. Composites with different contents of reinforcing particles (12 vol.%, 15 vol.% and 21 vol.%) and different mean particle diameter showed about ten times fewer cycles to failure than unreinforced 6061-T6. The fatigue limits were 145 MPa for unreinforced 6061-T6 and 115 MPa for the reinforced alloys. Large, broken particles could be observed as preferential sites for fatigue crack initiation. Near crack initiation, Al2O3 particles are unsuitable obstacles for short crack growth, but brittle fracture of the reinforcing component was observed; arrangement of particles in clusters favours the initial damage process in addition. In order to optimize the fatigue properties of 6061 aluminium alloys, fine Al2O3 particles should be used; a high content of reinforcing component is beneficial for increasing the stiffness of the alloy. Copyright (C) 1996 Elsevier Science Limited