J. Phys. Colloques 48 (1987) C3-761-C3-767
THE TEMPERATURE DEPENDENCE OF THE HIGH CYCLE FATIGUE PROPERTIES OF AN Al-Li-Cu-Mg ALLOYP.J.E. BISCHLER1 et J.W. MARTIN2
1 C.E.G.B., B.N.L., Berkeley, Glos. Great-Britain
2 Oxford University Department of Metallurgy and Science of Materials, Parks Road, GB-Oxford, OX1 3PH, Great-Britain
It is known that a post-solution treatment stretch gives a finer, more uniformly distributed S-phase when ageing Al-Li-Cu-Mg alloys. Fatigue S - N curves have been determined, and tensile tests have been carried out on stretched (P) and unstretched (N) samples of 8090 alloy in the peak-aged condition at temperatures of 288K, 358K and 425K. A fractographic comparison has been made of the fatigued samples in the two conditions. It is found that magnitude of the Endurance Ratio (of Endurance Limit to UTS) is relatively high, due to the homogenisation of slip by the S-phase, and is higher in the P than in the N material. A decline in Endurance Ratio with increase in temperature is observed in P material, but not in the N material. The results are discussed in terms of the dislocation interactions in the two microstructures, and is supported by previously observed differences in dynamic recovery characteristics between N and P material.