Fracture Behavior of SiC Whisker Reinforced Aluminum Alloy under Combined Tension/Torsion Loading at Room and Elevated Temperatures.

Abstract

This paper describes an investigation on the tensile and fatigue fracture behavior of an SiC whisker reinforced 6061 aluminum alloy fabricated by a squeeze casting process under combined tension/torsion loading at room and elevated temperatures. The tests were conducted under a load-controlled condition keeping a constant value of the combined stress ratio, α=τ/σ. Except for the elongation at failure, mechanical properties of the composite including fatigue strength were superior to those of an unreinforced 6061 alloy, not only under uniaxial loading, but also under combined tension/torsion loading. The static strength of the composite and the unreinforced matrix material showed good agreement with the Tsai-Hill failure criterion. Fatigue strength under αl1 was determined by maximum principal stress, whereas the strength under α>1 was determined by maximum equivalent stress. Fracture surfaces were closely examined with a scanning electron microscope, and the fracture mechanisms under combined tension/torsion loading were discussed.