Abstract
In this paper, smooth specimens of three aluminum alloys: AA 2219-T8, AA 2519-T8 and AA 2624-T351, were subjected to the same level of uniaxial (tension/compression) fatigue loading to compare their fatigue responses. Fractographic investigations of the failed specimens after fatigue loading was also conducted using a scanning electron microscope. The fatigue test results showed considerable differences in the fatigue lives of the three investigated alloys with AA 2219-T8 having the shortest fatigue life and AA 2624-T351 the longest fatigue life. The fractographic analysis showed that coalescence of micropores, microvoids, particles cleavage and microcracks are the predominant features in the fracture surface of AA 2219-T8. The fracture surface features of AA 2519-T8 revealed higher resistance to fatigue cracks nucleation and growth when compared to AA 2219-T8. The features depicted mainly partly ductile and partly brittle fracture. The AA 2624-T351 fracture surface features revealed noteworthy ductile failure mechanism. The results suggest a strong correlation between the surface fractographic features and the fatigue lives of the alloys. It is also observed that in addition to the yield strengths and ultimate tensile strengths, the total strain energy densities (SED) may provide a reasonable indication of the relative fatigue performance of the three alloys. AA 2219-T8 had the lowest SED and the lowest fatigue life, while AA 2624-T351 had the highest SED and the highest fatigue life. Thus, AA 2624-T351 would be the most suitable materials for components subjected to fatigue loading.
Highlights
The authors asserted that the determinations of fatigue life and cracks size and crack growth rates are critical for strategic safety evaluation process
Findings from this study revealed that Hot Isostatic Pressing (HIP) process led to immense reduction in fatigue resistance by about 40% for A356 and 70% for A204
The fatigue response of smooth specimens of AA 2219-T8, AA 2519-T8 and AA 2624-T351 were investigated in this work
Summary
Aluminum alloys have a proven 70-year record of continuously improvement in terms performance and production cost [1] The benefits of these alloys include their high specific strength, excellent corrosion resistance, high fracture toughness and fatigue crack growth resistance [2]-[8]. In the concluding remark of the paper, it was suggested that the surface roughness as well as the fatigue resistance of the alloy can be enhanced by using higher power and high absorption wavelength (such as λ =1.06 μm). The study revealed that addition of scandium refines the grain structure of the alloy, but yielded poor fatigue crack growth resistance and fatigue thresholds. Very long-life fatigue and near threshold fatigue crack growth response of 7075 and 6061 aluminum alloys in T6 condition were investigated by Wang et al [17]. During high crack growth rates, the observed voids were insignificant while stri-
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