Low cycle fatigue behavior of a SiCp reinforced aluminum matrix composite at ambient and elevated temperature

Abstract

Based on an investigation of low cycle fatigue life and cyclic stress response characteristics of SiC particulates reinforced pure aluminum and unreinforced matrix aluminum at 298 K and 441 K, the following observations were made. (1) Cyclic stress response of the unreinforced matrix aluminum, in the as-extruded condition, revealed initial cyclic hardening, cyclic stability and second hardening at ambient temperature. With a contrast, the unreinforced aluminum at elevated temperature showed progressively cyclic softening behavior without initial hardening. (2) The cyclic stress response characteristics of the composite were different from that of its unreinforced matrix at room temperature. In spite of the initial hardening, the composite showed progressive softening in most of the fatigue life. At elevated temperature the composite also displayed continuous cyclic softening behavior. The reason for the softening behavior probably was that the dislocation tangles in the composite specimen with a likely work-hardened status was not stable and could be changed under a cyclic loading. (3) The SiCp/Al composite and the unreinforced matrix followed the Coffin-Manson law. The low cycle fatigue resistance of the composite at room temperature was lower than that of the unreinforced matrix. A decrease in the fatigue endurance due to a rise in testmore » temperature was observed for the composite and the unreinforced matrix especially at low cyclic plastic strain ranges. The induction of fatigue life of the unreinforced aluminum was faster than that of the composite, so the fatigue resistance of the composite was stronger than that of the unreinforced aluminum under lower cyclic strain ranges at elevated temperature.« less