Low Cycle Fatigue of an Ultrafine Grained AA5083 Aluminum Alloy Composite Produced by Cryomilling

Abstract Low cycle fatigue (LCF) properties were investigated for a novel cryomilled AA5083 aluminum composite with duplex coarse and ultrafine grain sizes reinforced boron carbide particulates, referred to as trimodal material. Fully reversed cyclic tests conducted under plastic strain control at amplitudes from 0.15 0.6 pct using constant rate in servo-hydraulic testing system. A nonlinear elastic modulus was used calculate the contribution measured total strain. The LCF performance of this material is compared previous results unreinforced alloy bimodal size (85/15 CM/UM) its coarse-grained wrought counterpart, AA5083-H131. Stress response curves revealed slow hardening until failure associated presence particulate reinforcements. very small asymmetry between tension compression stresses reflects lack localization beyond initial cycles. 85/15 CM/UM alloys have similar superior low strength From Coffin-Manson plot, has shorter life than AA5083-H131 high amplitudes, but nearly identical amplitudes. Microcracks observed near dominant crack on specimen surfaces failure. Back-scattered images that particulates altered propagation direction; cracks always propagated around particulates.