Strain localization and damage development in 2060 alloy during bending

Abstract

The microstructure evolution and damage development of the third-generation Al–Li alloy 2060 (T8) were studied using in situ bending tests. Specimens were loaded with a series of punches of different radii, and the microstructure evolution was studied by scanning electron microscopy, electron backscatter diffraction, and digital image correlation (DIC) methods. The evolution of the microscopic fracture strain distribution and microstructure in 2060 alloy during bending was characterized, where the dispersion distribution of precipitates was recorded by backscattered electron imaging and later inputted into a DIC system for strain calculations. The experimental results showed that strain localization in the free surface of bent specimens induced damage to the microstructure. The region of crack initiation lies on the free surface with maximum strain, and the shear crack propagates along the macro-shear band in the early stages of bending. Crack propagation in the later stages was interpreted on the basis of the conventional mechanism of ductile fracture.

Keywords

aluminum-lithium alloys / deformation / microstructure / fracture / bending tests

References

[1] Karabin L.M., Bray G.H., Rioja R.J., Venema G. Al-Li-Cu-Mg-(Ag) products for lower wing skin applications. ICAA13: 13th International Conference on Aluminum Alloys, 2012 529.

[2] Rioja R.J., Liu J. The Evolution of Al?Li base products for aerospace and space applications. Metall. Mater. Trans. A, 2012, 43(9): 3325.

[3] Zheng Z.Q., Li J.F., Chen Z.G., Li H.Y., Li S.C., Tan C.Y. Alloying and microstructural evolution of Al?Li alloys. Chin. J. Nonferrous Met., 2011, 21(10): 2337.

[4] Davidkov A., Petrov R.H., De Smet P., Schepers B., Kestens L.A.I. Microstructure controlled bending response in AA6016 Al alloys. Mater. Sci. Eng. A, 2011, 528(22-23): 7068.

[5] Marzouk M., Jain M., Shankar S. Effect of Sr-modification on the bendability of cast aluminum alloy A356 using digital image correlation method. Mater. Sci. Eng. A, 2014, 598, 277.

[6] Nemati J., Majzoobi G.H., Sulaiman S., Baharudin B.T.H.T., Azmah Hanim M.A. Effect of equal channel angular extrusion on Al-6063 bending fatigue characteristics. Int. J. Miner. Metall. Mater., 2015, 22(4): 395.

[7] Hu X.H., Jain M., Wu P.D., Wilkinson D.S., Mishra R.K. A macro-micro-multi-level modeling scheme to study the effect of particle distribution on wrap-bendability of AA5754 sheet alloys. J.^Mater. Process. Technol., 2010, 210(9): 1232.

[8] Becker R. An analysis of shear localization during bending of a polycrystalline sheet. J. Appl. Mech., 1992, 59(3): 491.

[9] Kuroda M., Tvergaard V. Effects of texture on shear band formation in plane strain tension/compression and bending. Int. J Plast., 2007, 23(2): 244.

[10] Davidkov A., Jain M.K., Petrov R.H., Wilkinson D.S., Mishra R.K. Strain localization and damage development during bending of Al-Mg alloy sheets. Mater. Sci. Eng. A, 2012, 550, 395.

[11] Mattei L., Daniel D., Guiglionda G., Klöcker H., Driver J. Strain localization and damage mechanisms during bending of AA6016 sheet. Mater. Sci. Eng. A, 2013, 559, 812.

[12] Roux S., Réthoré J., Hild F. Digital image correlation and fracture: an advanced technique for estimating stress intensity factors of 2D and 3D cracks. J. Phys. D, 2009, 42(21): 214004.

[13] Lemmen H.J.K., Alderliesten R.C., Benedictus R., Hofstede J.C.J., Rodi R. The power of Digital Image Correlation for detailed elastic-plastic strain measurements. International Conference on Engineering Mechanics, Structure, Engineering Geology, 2008 73.

[14] Corr D., Accardi M., Graham-Brady L., Shah S. Digital image correlation analysis of interfacial debonding properties and fracture behavior in concrete. Eng. Fract. Mech., 2007, 74(1-2): 109.

[15] Yang W.Y., Qiang W.J. Mechanical Behavior of Materials, 2009, Beijing, Chemical Industry Press, 71.

[16] Datsko J., Yang C.T. Correlation of bendability of materials with their tensile properties. J. Manuf. Sci. Eng., 1960, 82, 309.

[17] Iacono C., Sinke J., Benedictus R. Prediction of minimum bending ratio of aluminum sheets from tensile material properties. J. Manuf. Sci. Eng., 2010, 132(2): 021001.

[18] Takeda H., Hibino A., Takata K. Influence of crystal orientations on the bendability of an Al–Mg–Si alloy. J. Jpn. Inst. Light Met., 2010, 60(5): 231.

[19] Tvergaard V., Needleman A. Shear band development in polycrystals. Proc. R. Soc. A, 1993, 443(1919): 547.

[20] Gregson P.J., Flower H.M. Microstructural control of toughness in aluminium-lithium alloys. Acta Metall., 1985, 33(3): 527.

[21] Koss D.A., Chan K.S. Fracture along planar slip bands. Acta Metall., 1980, 28(9): 1245.

[22] Glazer J., Verzasconi S.L., Sawtell R.R., Morris J.W. Mechanical behavior of aluminum-lithium alloys at cryogenic temperatures. Metall. Trans. A, 1987, 18(10): 1695.

[23] Vasudévan A.K., Doherty R.D. Grain boundary ductile fracture in precipitation hardened aluminum alloys. Acta Metall., 1987, 35(6): 1193.

[24] Evensen J.D., Ryum N., Embury J.D. The intergranular fracture of Al-Mg-Si alloys. Mater. Sci. Eng., 1975, 18(2): 221.