Abstract
Torsional fatigue tests of SiC whisker or SiC particulate reinforced 6061-T6 aluminum matrix composite (SiCw/Al or SiCp/Al), fabricated by a high pressure infiltration method, were performed. From a comparison with the properties of the monolithic aluminum alloy, it became clear that the torsional fatigue strength of 6061Al alloy was increased by reinforcing either with SiC whiskers or SiC particulates. Unlike strong orientation dependency of the tensile strength or fatigue strength in rotating bending, no orientation dependency was observed in the torsional fatigue strength of the SiCw/Al with highly aligned whiskers. In the SiCp/Al, cracks both parallel and transverse to the axial direction of test piece were observed. On the other hand, cracks in the SiCw/Al were always formed parallel to the direction of aligned whiskers. That is, cracks parallel to the axis were observed in the L oriented specimen whose axis was parallel to the direction of aligned whiskers and cracks transverse to the axis were observed in the T oriented specimen whose axis was transverse to the aligned whiskers. Importance of shear deformation in initiating fatigue cracks was clarified.
