Fatigue, Fatigue Crack Propagation and Mechanical Fracture Behaviour of Laser Beam-Welded AZ31 Magnesium Sheets

Abstract:

Weight reduction is the main driving force in automotive and aircraft structural design. As a result, magnesium alloys, with their high potential for lightweight construction, have attracted a considerable amount of industrial attention. The determining criterion for the structural applications of magnesium alloys is the availability of efficient joining technologies for the construction of lightweight structures and the availability of reliable data for the assessment of their damage tolerance behaviour. Laser beam welding (LBW), as a high-speed and easily controllable process, allows the welding of complex geometric forms that are optimised in terms of mechanical stiffness, strength, production velocity and visual quality. The work accomplished in this study addresses the challenges of the LBW process for typical joint configurations using the magnesium alloy AZ31HP: butt joints, T joints and overlap joints. LBW processes were developed for use with a 3.3-kW Nd:YAG laser to optimise the mechanical performance of such joints with respect to tensile strength, fatigue, fatigue crack propagation and mechanical fracture behaviour. The relationships between the LBW process and the microstructural and mechanical properties of welds were established. Compared to state-of-the-art aerospace alloys, AZ31HP demonstrates that magnesium alloys have potential for use in structural applications, with AZ31HP being comparable to AA2024T351 and AA6061T6. Welded AZ31HP exhibits better crack resistance than the base material, so fully welded integral structures made from magnesium alloys can be used in lightweight construction.

• Periodical: Materials Science Forum (Volumes 783-786)
• Pages: 2310-2315
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.783-786.2310
• Online since: May 2014
• Authors: Nikolai Kashaev*, Stefan Riekehr, Manfred Horstmann, Volker Ventzke
• Keywords: AZ31, Fatigue, Fracture Toughness, Laser Beam Welding, Magnesium, R-Curve

References

[1] C. Blawert, N. Hort and K.U. Kainer, Trans. Indian Inst. Met. 57 (2004) 397-408.

[2] M. Easton, A. Beer, M. Barnett, Ch. Davies, G. Dunlop, Yv. Durandet, S. Blacket, T. Hilditch and P. Beggs, JOM 60 (2008) 57-62.

DOI: 10.1007/s11837-008-0150-8

[3] EU FP6 project AEROMAG, 2005-2008, Contract AST4-CT-2005-516152, Information on http: /cordis. europa. eu/search/index. cfm?fuseaction=proj. document&PJ_RCN=7978073.

[4] H. Somekawa, T. Mukai, J. Alloys and Compounds 417 (2006) 209-213.

[5] V. Ventzke, S. Riekehr, M. Kocak, Mat. -wiss. u. Werkstofftech. 39 (2008) 1-13.

[6] R.S. Coelho, Joining of light-weight materials by friction stir and laser beam welding, Dissertation, Bochum, (2009).

[7] P. Kanzow, Laser beam welded T-joints of the magnesium alloy AZ31, Diploma Thesis, Helmholtz-Zentrum Geesthacht, Geesthacht, (2011).

DOI: 10.22449/1573-160x-2020-6-631-658

[8] S. Riekehr, V. Ventzke, M. Horstmann, N. Kashaev, Fatigue and fatigue crack propagation of Nd: YAG laser beam-welded magnesium AZ31-HP sheet material, In proceedings of the 9th International Conference on Magnesium Alloys and their Applications, Vancouver, 2012, 827-832.

DOI: 10.4028/www.scientific.net/msf.783-786.2310

[9] S. Giammarinaro, S. Riekehr, B. Previtali, M. Hibben and N. Kashaev, Mechanical performance of laser welded and resistance spot welded overlap joints from magnesium AZ31B sheets, In Proceddings of the International Conference on Joining Materials, Helsingør, (2013).

DOI: 10.4028/www.scientific.net/msf.828-829.298

[10] D. Steglich, J. Bohlen, X. Tian, S. Riekehr, N. Kashaev, S. Bargmann, D. Letzig, K. -U. Kainer, N. Huber, Materials Science Forum, Light Metals Technology Conference, LMT 2013. 765 (2013).

DOI: 10.4028/www.scientific.net/msf.765.590

[10] W. Danzer, Mat. -wiss. u. Werkstofftech. 2005, 36, No. 6; DOI: 10. 1002/mawe. 200500881.

[11] Oe. Karakas, C. Morgenstern, C.M. Sonsino, Int. Journal of Fatigue 30 (2008) 2210-2219; DOI: 10. 1016/j. ijfatigue. 2008. 05. 017.

[12] R.C. Zeng, Y.B. Wu, W. Ke, E.H. Han, Mat. Science and Engineering. A509 (2009) 1-7, DOI: 10. 1016/j. msea. 2009. 01. 013.

[13] K. -H. Schwalbe, J. Heerens, U. Zerbst, H. Pisarsik, M. Kocak, The GKSS test procedure for determining the fracture behaviour of materials, Report Nr. GKSS 2002/24, Geesthacht, (2002).