Fatigue crack growth behaviour in aluminium alloy 7475 under different aging conditions

The effects of aging temperature and aging time on fatigue crack growth resistance have been studied for a 7475 (Al - Zn - Mg based) aluminium alloy. The alloy was tested in the underaged, peak aged, and overaged conditions after aging at 120 and 160 degreesC. Fatigue crack propagation tests were conducted in laboratory air using compact tension specimens in L-S orientation, under constant amplitude sinusoidal loading with an R ratio of zero. Results are discussed on the basis of resultant microstructures, fatigue crack growth rate diagrams and fractographic analysis. At 120 degreesC, a considerable effect of aging time on crack velocities at high stress intensities was seen. However, at 160 degreesC no significant dependency of crack growth rate on aging time was observed. The fatigue performance of overaged specimens was better for both aging temperatures. Also, lower aging temperature resulted in a more resistant structure against fatigue crack growth. Fractographic inspection showed that intermetallic particles play an important role in the crack growth behaviour of the Al - Zn - Mg alloy.


SARIOGLU, F; ABACHI, P; DORUK, M (Springer Science and Business Media LLC, 1993-03-15)
Crack growth tests at 150-degrees-C under constant load conditions were performed on compact tension specimens of 7050-T73651 aluminium alloy. The d.c. potential drop method was employed to monitor crack lengths throughout the tests. Fracture mechanics parameters such as the stress intensity factor (K) and energy-rate line integral (C*) were used to establish correlation with the crack propagation rates. As a result of experiments it was found that crack growth rates (da/dt) versus K, over discrete ranges o...
Electrical conductivity of polypyrrole films at a temperature range of 70 K to 350 K
Kaynak, A (Elsevier BV, 1998-01-01)
The de conductivity of electrochemically synthesized polypyrrole films doped from light to intermediate levels with p-toluene sulfonic acid was measured in the temperature range of 77 to 300 K, using a modified four-probe rig. Plots of de conductivity vs. temperature were parameterized by fitting Mott's Variable Range Hopping conduction model. The localization length of localized electrons was assumed to be 3 Angstrom, which is approximately equal to the length of a pyrrole monomer. Mott parameters of polyp...
Electrical conductivity and Hall mobility in p-type TlGaSe2 crystals
Qasrawi, AF; Hasanlı, Nızamı (Elsevier BV, 2004-07-02)
Systematic dark electrical conductivity and Hall mobility measurements have been carried out in the temperature range of 200-350 K on p-type TlGaSe2 crystals. The analysis of the temperature-dependent electrical conductivity and carrier concentration reveals the extrinsic type of conduction with an acceptor impurity level located at 0.33 eV, and donor and acceptor concentrations of 9.0 x 10(15) and 1.3 x 10(16) cm(-3), respectively. A hole and electron effective masses of 0.520m(0) and 0.325m(0), respective...
Transient and steady state photoelectronic analysis in TlInSe2 crystals
QASRAWI, ATEF FAYEZ HASAN; Hasanlı, Nızamı (Elsevier BV, 2011-08-01)
The temperature and illumination effects on the transient and steady state photoconductivities of TlInSe2 crystals have been studied. Namely, two recombination centres located at 234 and at 94 meV and one trap center located at 173 meV were determined from the temperature-dependent steady state and transient photoconductivities, respectively. The illumination dependence of photoconductivity indicated the domination of sublinear and supralinear recombination mechanisms above and below 160 K, respectively. Th...
Mechanical and microstructural evaluations of hot formed titanium sheets by electrical resistance heating process
Ozturk, Fahrettin; Ece, Remzi Ecmel; Polat, Naki; Koksal, Arif; Evis, Zafer; Polat, Aytekin (Elsevier BV, 2013-08-20)
In this study, effect of temperature in the electrical resistance heating process on mechanical properties and microstructures of commercially pure titanium grade 2 (CP2) and Ti-6Al-4V (T64) alloy sheets was investigated. Sheets were successfully heated by the electric resistance heating process, and their mechanical properties and microstructures were evaluated. Ductilities of both materials were increased significantly after 400 degrees C. Results indicate that no significant change was observed in grain ...
Citation Formats
R. Gürbüz, “Fatigue crack growth behaviour in aluminium alloy 7475 under different aging conditions,” MATERIALS SCIENCE AND TECHNOLOGY, pp. 1539–1543, 2001, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/35122.