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Title: Environmentally assisted fatigue response of Al-Cu-Mg-Mn with SiC particulate metal matrix composites
Author: Uygur, I.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 1999
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Experimental research has been carried out with the purpose of evaluating the tensile properties, stress and strain control fatigue properties and, crack propagation behaviour of a particulate reinforced metal matrix composite. Fractographic examination has also been undertaken of the powder metallurgy processed 2124 Al-alloy with two volume fractions (17 and 25vol%) and different particle sizes (2.5μm and 15μm) silicon carbide particles (SiCp). The present study shows that tensile properties of composites significantly improve with the incorporation of hard, brittle ceramic particles. The composite materials were cyclically deformed over a range of constant stress amplitudes at R=0.1 and R=0.5 using a variety of notch geometries in air and elevated temperatures. Results indicated that for a given aged condition (T4), load controlled fatigue lives of the composites are significantly improved compared with the unreinforced base alloy. However the severity of a notch, i.e. increased stress concentration factor and elevated temperatures shift down the S-N curves of the 2124 25vol% SiCp (AMC225) composite material. The effects of particle size and volume fraction on strain controlled fatigue behaviour were evaluated for a variety of composite materials at different strain range levels. An increased volume fraction of particles reduces fatigue lives due to the lower monotonic ductility of the AMC225 composite which showed some degree of softening at R=-1, but stable behaviour at the R=0 conditions under strain loading. At R=0.5 the composite cyclically hardened. On the basis of these results, fatigue life predictions for the notch geometries have been made by using a critical strain approach.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available