FATIGUE CRACK-PROPAGATION OF SIC WHISKER REINFORCED 6061 ALUMINUM-ALLOY COMPOSITE

The fatigue strength and fatigue crack propagation (FCP) behavior of SiC whisker reinforced 6061-T6 aluminum-matrix composite fabricated by the high pressure infiltration method were studied. In addition to tensile strength, fatigue strength was increased by whisker reinforcement. However, because of the highly aligned whiskers to the L direction caused by the extrusion process they showed strong orientation dependence. The L orientation showed higher strengths than the T orientation. The FCP resistance in T-L or T-T oriented composites was lower than that in unreinforced 6061-T6 alloy, while in L-T oriented composites, deflected FCP occurred and great increases in the FCP resistance resulted by whisker reinforcement when comparison was made by the mode I stress intensity factor. Fractographic investigation was also made to clarify the fatigue mechanism of this composite.