The effect of chromic acid anodizing (CAA) surface treatment on 7050 T7451 aluminum alloy was presented in this study in terms of fatigue behavior. CAA is a treatment against corrosion by producing aluminum oxide layer (Al2O3) at the surface. However, fatigue performance of 7050 T7451 is affected by the coating. In this study, eight different CAA processes were examined with regard to etching stage of pre-treatments by using an alkaline etchant and/or acid etchants with various immersion times. Optical microscopic examinations were applied in order to determine pitting characteristics for the selection of CAA process parameters before fatigue tests. A CAA process was selected among eight processes in terms of pitting characteristics in order to apply fatigue specimens. Four fatigue test groups were determined to investigate bare condition of 7050 T7451 and sub-stages of the CAA particularly. Constant amplitude axial fatigue tests were conducted on specimens at 91 Hz at stress ratio (R) -1 until run-out criteria, which was 106 cycles. Fatigue life reduction was determined due to pretreatments of CAA. Fracture surfaces of the specimens were examined by scanning electron microscope (SEM) to investigate morphology and crack initiation sites.
About the authors
Çağrı İlhan, born in 1991, received his bachelor’s and master’s degree at Middle East Technical University, Ankara, Turkey in 2015 and 2019, respectively. He worked as a R&D engineer at CMS Light Alloy Wheels in Izmir,Turkey for a year. He has worked as a Rotating Wing Test Engineer at Turkish Aerospace in Ankara, Turkey since 2016. His area of research focuses on mechanical testing from coupon level to full scale level of aerospace products, condition monitoring and data acquisition. His extracircular activities are guitar, travelling, freeletics and basketball.
Prof. Rıza Gürbüz received his phD degree at Middle East Technical University (METU), Ankara, Turkey in 1987. He received his Assistant professor and Associate Professor titles at METU in 1988 and 1991, respectively. He has worked as a professor lecturer and researcher at the Middle East Technical University in Ankara, Turkey since 2003, continuing his academic life. His research interests are focused on mechanical properties, mechanical testing, destructive testing of welds, fatigue of materials, corrosion, aluminum alloys, denture materials, failure analyses. His extracircular activities are photography, volleyball, camping, yoga, zen, wine, swimming, travelling.
1 M. Shahzad, M. Chaussumier, R. Chieragatti, C. Mabru, F. Rezai-Aria: Surface characterization and influence of anodizing process on fatigue life of Al 7050 alloy, Materials Design 32 (2011), No. 6, pp. 3328-3335 DOI:10.1016/j.matdes.2011.02.02710.1016/j.matdes.2011.02.027Search in Google Scholar
2 F. C. Campbell: Manufacturing technology for aerospace structural materials, 1st Ed., Elsevier, Amsterdam, The Netherlands (2006) DOI:10.1016/B978-185617495-4/50011-110.1016/B978-185617495-4/50011-1Search in Google Scholar
3 H. Asoh, K. Nishio, M. Nakao, T. Tamamura, H. Masuda: Conditions for fabrication of ideally ordered anodic porous alumina using pretextured Al, Journal of the Electrochemical Sociecty 148 (2001), No. 4, pp. 15-24 DOI:10.1149/1.135568610.1149/1.1355686Search in Google Scholar
4 S. Mechanics, L. Molent, D. Science, S. Barter, D. Science, R. Jones: Multiscale fatigue crack initiation and propagation of engineering materials: Structural integrity and microstructural worthiness, 1st Ed., Springer, Berlin, Germany (2008), pp.66-83Search in Google Scholar
5 ASTM E8: Standard test methods for tension testing of metallic materials, No. 13a, ASTM International, West Conshohocken, Pennsylvania, USA (2009)Search in Google Scholar
6 ASTM B244: Standard test method for measurement of thickness of anodic coatings on aluminum and of other nonconductive coatings on nonmagnetic basis metals with eddy-current instruments, ASTM International, West Conshohocken, Pennsylvania, USA (2017)Search in Google Scholar
7 ASTM E466: Standard practice for conducting force controlled constant amplitude axial fatigue tests of metallic materials, ASTM International, West Conshohocken, Pennsylvania, USA (2002)Search in Google Scholar
8 AMS 4050: Aerospace material specification (AMS 4050) of aluminum alloy, SAE International Group, Warrendale, Pennsylvania, USA (2016)Search in Google Scholar
9 R. Wagener, T. Melz: Fatigue life curve – A continuous Wöhler curve from LCF to VHCF, Materials Testing 60 (2018), pp. 924-930 DOI:10.3139/120.11123310.3139/120.111233Search in Google Scholar
10 S. A. Barter, P. K Sharp, G. Holden, G. Clark: Initiation and early growth of fatigue cracks in an aerospace aluminum alloy, Fatigue Fracture Engineering Materials Structure 25 (2001), pp. 111-125 DOI:10.1046/j.1460-2695.2002.00482.x10.1046/j.1460-2695.2002.00482.xSearch in Google Scholar
11 J. R. Davis: ASM specialty and handbook aluminum and aluminum alloys, ASM International, Materials Park, Ohio, USA (1993), pp. 3-12Search in Google Scholar
© 2021 Walter de Gruyter GmbH, Berlin/Boston, Germany