Effect of Different Forms of Application of a Laser Surface Treatment on Fatigue Crack Growth of an AA6013-T4 Aluminum Alloy
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This work analyzes the effect of surface-localized laser heating treatment on the fatigue crack growth (FCG) rate on region II of the sigmoidal da/dN × ΔK curve of an aerospace-grade AA6013-T4 aluminum alloy sheet with 1.3 mm thickness. The influence on microstructure changes is also evaluated. Aiming to improve the FCG resistance without changing the mechanical behavior of the alloy, a Yb:fiber laser beam is defocused to generate a laser spot diameter of 2 mm, using 200 W power and a laser speed of 2 mm/s. Two laser lines are applied over fatigue C(T) specimens in two different forms: on only one and on both lateral specimen surfaces. Guinier–Preston zones, dispersoids and coarse constituent particles are found on the base material. On the heat-treated material, the same precipitates and also β′ and Q′ precipitates are found. These microstructural variations due to the laser thermal cycle, together with the presence of induced compressive residual stresses, improved the fatigue behavior of the material. The FCG retardation is optimized when two laser lines were applied on both lateral surfaces of the specimen.
Keywordsaluminum alloy fatigue crack growth laser surface treatment microstructure residual stresses
The authors would like to acknowledge the Center of Microscopy at the Universidade Federal de Minas Gerais (Brazil) for providing the equipment and technical support for experiments involving transmission electron microscopy. C.M. Gonçalves would like to acknowledge CAPES for providing her financial support.
- 1.I. Polmear, D. StJohn, J.F. Nie, and M. Qian, Light Alloys—Metallurgy of the Light Metals, 5th ed., Elsevier, Amsterdam, 2017Google Scholar
- 2.J.E. Hatch, Aluminum—Properties and Physical Metallurgy, American Society for Metals, Materials Park, 1984Google Scholar
- 3.R.K. Nalla, I. Altenberger, U. Noster, G.Y. Liu, B. Scholtes, and R.O. Ritchie, On the Influence of Mechanical Surface Treatments—Deep Rolling and Laser Shock Peening—On the Fatigue Behavior of Ti-6Al-4V at Ambient and Elevated Temperatures, Mater. Sci. Eng. A, 2003, 355, p 216–230CrossRefGoogle Scholar
- 12.D. Schnubel, Laser Heating as Approach to Retard FCG in Aircraft Aluminium Structures. PhD Thesis. Hamburg’s University. Germany. 2012, p 115Google Scholar
- 15.A. Groth, M. Horstmann, N. Kashaev, and N. Huber, Design of Local Heat Treatment for Crack Retardation in Aluminium Alloys. 1st International Conference on Structural Integrity. Procedia Eng., 2015, 114, p 271–276Google Scholar
- 23.M. Bloeck, Aluminium Sheet for Automotive Applications, In: Advanced Materials in Automotive Engineering, Woodhead Publishing, 2012Google Scholar
- 28.Standard Test Method for Microindentation Hardness of Materials 1, E384-17, ASTM, 2018, p 40Google Scholar
- 29.E. Yanase, K.N. Vlad, M.I.R. Zolotarev, K. Nishio, Y. Kusum, K. Arai, and S. Nakagawa, Sin2Ψ Stress Measurement Method with Maintaining Probing Depth, J. Neurosci. Res., 2001, 9, p 273–279Google Scholar
- 30.Standard Test Method for Measurement of FCG Rates, E647 – 13, ASTM, 2014, p 49Google Scholar
- 43.T.L. Anderson, Fracture Mechanics—Fundamentals and Applications, 3rd ed., CRC Press, Boca Raton, 2005Google Scholar