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Fatigue crack growth of AA2219 under different aging conditions |
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| Authors: | V.M.J. SharmaK. Sree Kumar B. Nageswara Rao S.D. Pathak |
| Affiliation: | a Material Characterisation Division, Materials and Metallurgy Group, Vikram Sarabhai Space Centre, Trivandrum 695 022, India b Structural Analysis and Testing Group, Vikram Sarabhai Space Centre, Veli Research Complex, Indian Space Research Organisation, Trivandrum 695 022, India c Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600 036, India |
| Abstract: | The fatigue crack growth of commercial AA2219 has been examined under different aging treatments, namely, naturally aged (NA), under aged (UA), peak aged (PA) and over aged (OA) conditions. From the near threshold stress intensity range (ΔKNTH), the alloy in the NA condition is found to have the highest resistance to fatigue crack initiation. The crack growth rate increases and the near threshold stress intensity range decreases with advancing aging. This observation is found to be consistent with lower levels of crack closure and decreasing levels of tortuosity in crack path for PA and OA tempers. The inhomogeneous transcrystalline slip in the UA condition results in the slower crack growth at low stress intensity range (ΔK). The fracture morphology changes from crystallographic facets near the threshold region to clearly developed ductile striations in the Paris power-law regime to microvoid coalescence in the high ΔK regions. |
| Keywords: | Fatigue crack growth Aging Aluminum alloys Striations Threshold stress intensity range |
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