Influence of chemical liquids on the fatigue crack growth of the AZ31 magnesium alloy

Abstract

The fatigue crack growth behavior of an AZ31 magnesium alloy was investigated by comparing the effect of zirconate and phosphate chemical liquids. The morphology, components, and phase compositions of the chemical depositions at the fatigue crack tip were analyzed by employing scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD), respectively. For samples with and without the chemical liquids, their stress-intensity factor values at the fatigue crack tip were compared by using a stress-strain gauge. The results demonstrated that a zirconate film (Zr _xO _y·Zn _xO _y) and a phosphate film (Zn₃(PO₄)₂·4H₂O and MgZnP₂O₇) could be formed on the fatigue crack-surface at the fatigue crack tip. The stress distribution was changed because of the chemical depositions and the causticity of the chemical liquids. This could decrease the stress-intensity factor value and thus effectively cause fatigue crack closure, which reduces the fatigue crack growth rate. Moreover, it was found that the fatigue crack closure effect of zirconates was more positive than that of phosphates.

Keywords

magnesium alloys / fatigue cracks / crack closure / deposition / fatigue crack propagation

References

[1] Chen H. The research of magnesium alloy and application in automotive about light weight. Technol. Dev. Enterprise, 2009, 28(11): 17.

[2] Nan Z., Ishihara S., Goshrna L., Nakanishi R. Scanning probe microscope observations of fatigue process in magnesium alloy AZ3l near the fatigue limit. Scripta Mater., 2004, 50(4): 429

[3] Marya M., Hector L.G., Verma R., Tong W. Microstructural effects of AZ31 magnesium alloy on its tensile deformation and failure behavior. Mater. Sci. Eng. A, 2006, 418(1–2): 341

[4] Park S.H., Hong S.G., Bang W., Lee C.S. Effect of anisotropy on the low-cycle fatigue behavior of rolled AZ31 magnesium alloy. Mater. Sci. Eng. A, 2010, 527(3): 417

[5] Nascimento L., Yi S., Bohlen J., Fuskova L., Letzig D., Kainer K.U. High cycle fatigue behaviour of magnesium alloys. Procedia Eng., 2010, 2(l): 743

[6] Begum S., Chen D.L., Xu S., Luo A.A. Effect of strain ratio and strain rate on low cycle fatigue behavior of AZ31 wrought magnesium alloy. Mater. Sci. Eng. A, 2009, 517(1–2): 334

[7] Ishihara S., Nan Z.Y., Goshima T. Effect of microstructure on fatigue behavior of AZ31 magnesium alloy. Mater. Sci. Eng. A, 2007, 468-470(15): 214

[8] Zeng R.C., Han E.H., Liu L., Xu Y.B., Ke W. Effect of rolled microstructure on fatigue properties of magnesium alloy AM60. Chin. J. Mater. Res., 2003, 17(3): 241.

[9] Zeng R.C., Han E.H., Ke W. Fatigue and corrosion fatigue of magnesium alloys. Mater. Sci. Forum, 2005, 488–489, 721

[10] Shih T.S., Liu W.S., Chen Y.J. Fatigue of as-extruded AZ61A magnesium alloy. Mater. Sci. Eng. A, 2002, 325(1–2): 152

[11] Bag A., Zhou W. Tensile and fatigue behavior of AZ91D magnesium alloy. J. Mater. Sci. Lett., 2001, 20, 457

[12] Kobayashi Y., Shibusawa T., Ishikawa K. Environmental effect of fatigue crack propagation of magnesium alloy. Mater. Sci. Eng. A, 1997, 234–236, 220

[13] Liu Z., Li Y.C., Wang Z.G., Liu Z.Y. Influence of load frequency and heat treatment on fatigue crack propagation rate of die-casting alloy AZ91HP. J. Aeronaut. Mater., 2000, 20, 7.

[14] Sajuri Z.B., Miyashita Y., Mutoh Y. Effect of stress ratio on fatigue crack growth behavior of magnesium alloys. Mater. Sci. Forum, 2003, 419–422, 81

[15] Zeng R.C., Han E.H., Ke W., Dietze W., Kainer K.U., Atrens A. Influence of microstructure on tensile properties and fatigue crack growth in extruded magnesium alloy AM60. Int. J. Fatigue, 2010, 32, 411

[16] Zeng R.C., Xu Y.B., Ke W., Han E.H. Fatigue crack propagation behavior of as-extruded magnesium alloy AZ80. Mater. Sci. Eng. A, 2009, 509, 1

[17] Fan H.L., Chen P. Crack arrest effect in thin plates. Acta Armamentarii., 2005, 26(6): 791.

[18] Bai X.Z., Hu Y.D., Tan W.F. Advance of the study of crack prevention by the electromagnetic heat effect. Adv. Mech., 2000, 30(4): 546.

[19] Xiao F.R., Bai X.Z., Qiao G.Y., Luan J.Y. Influence of electromagnetic heat effect on microstructure and crack arrest of 35 steel. Trans. Met. Heat Treat., 2001, 22(2): 56.

[20] Fu Y.M., Zheng L.J., Bai X.Z. Experimental research on crack arrest in metal die using electromagnetic heating. J. Exp. Mech., 2004, 19(4): 488.

[21] Sha G.Y., Liu R.T., Liu D.K., Jiang F.C. Fracture and arrest in 907A steel under stress wave loads at −20°C. J. Harbin Eng. Univ., 2001, 22(1): 96.

[22] Ishihara S., Goshima T., Yoshimoto Y., Sabu T., McEvily A.J. The influence of the stress ratio on fatigue crack growth in a cermet. J. Mater. Sci., 2000, 35(22): 5661

[23] Zeng R.C., Ke W., Han E.H. Influence of load frequency and ageing heat treatment on fatigue crack propagation rate of as-extruded AZ61 alloy. Int. J. Fatigue, 2009, 31, 463

[24] Ren A.G., Wang X.J., Ding J. Research of laser-melt-repairing technology. Surf. Technol., 2006, 35(2): 69.

[25] Shin C.S., Cai C.Q. A model for evaluating the effect of fatigue crack repair by the infiltration method. Fatigue. Fract. Eng. Mater. Struct., 2000, 23(10): 835

[26] GB/T 6398-2000, Standard Test Method for Fatigue Crack Growth Rates of Metallic Materials.

[27] Suresh S. Fatigue of Materials, 1998, Cambridge, Cambrige University Press, 609