Occurrence of Defects in Laser Beam Welded Al-Cu-Li Sheets with T-Joint Configuration

Higashi, André Luiz de Carvalho; Lima, Milton Sérgio Fernandes de

doi:10.5028/jatm.2012.04044212

Abstract:

In the aerospace industry, laser beam welding has been considered as one of the most promising routes among the new manufacturing processes. Substitution of riveting by laser beam welding of aircraft structures has contributed to weight and cost savings. Concurrently, new aluminum alloys have been developed with the addition of lithium with better mechanical properties and lower density. The Al-3.5%Cu-1.1%Li alloy (AA2198) is one of these new generation alloys. However, laser beam welding of Al-alloys expectations might be greatly reduced by the occurrence of two main defects: porosity and hot cracking. Porosity is mainly caused by the entrapment of lithium gases, followed by rapid solidification. On the other hand, hot cracking happens due to the conjunction of tensile stresses, which are transmitted to the mushy zone by the coherent solid underneath, and to an insufficient liquid feeding to compensatefor the volumetric changes. This work intended to contribute towards the knowledge of AA2198 'welding metallurgy, utilizing a 2-kW-ytterbium-dopedfiber laser. The T-joint configuration welds were performed autogenously or with the addition of an AA4047 filler ribbon. Ali the weld beads presented high porosity level, but with a decreasing tendency when welding from both sides. The use of the filler material could solve hot cracking problem. The best results are observed using two runs (both sides) with filler and a speed of 2 m/min and power of 1,200 W. The T-pull tensile strength obtained under these conditions was 178 MPa, which is below the tensile strength of the unwelded AA2198 sheet but higher than the AA6013 welded in similar conditions.

Keywords:
Laser; Laser beam welding; Aluminum alloys; Aerospace

Full text available only in PDF format.

REFERENCES

ASM - American Society of Materials, 1993, "Metals Handbook - Volume 6: Welding, Brazing, and Soldering", 10nd ed., Metals Park (Ohio), ASM International, pp. 1392-1393.
Bordesoules, I. et al, 2007, "Trends in developments of Aluminium solutions for aerospace applications", In: Proceedings of the European Workshop on Short Distance Welding Concepts for Airframes frames - WEL-AIR, Hamburg, 13-15 june 2007, CD-Rom.
Campbell, J., 2003, "Castings", 2nd ed., Oxford: Elsevier Pergamon, 332p.
Clyne, T.W. and Davies G.J., 1975, "A Quantitive Solidification Test for Casting and An Evaluation of Cracking in Aluminium-Magnesium Alloys", The British Foundryman, Vol. 68, pp. 238-254.
Drezet, J.M. et al, 2008, "Crack-free aluminium alloy welds using a twin laser process, In: 61st International Conference of the International Institute of Welding", Graz. Safety and reliability of welded components in energy and processing industry. Graz (Áustria), TU-Graz, pp. 87-94.
Duarte, I. and Banhart, J., 2000, "A study of aluminium foam formation-kinetics and microstructure", Acta Materialia, Vol. 48, pp. 2349-2362.
King, D. et al, 2009, "Advanced aerospace materials: past, present and future, Aviation and The Environment", Vol. 3, pp. 22-27.
Lima, M.S.F. et al, 2000, "Advanced laser welding process", European patent no. 01810986.8.
Mangalgiri, P.D., 1999, "Composite materials for aerospace applications", Bulletin of Materials Science, Vol. 22, pp. 657-664.
Page, A.J. and Sear, R.P., 2006, "Heterogeneous Nucleation in and out of Pores", Physical Review Letters, Vol. 97, pp. 065701-1-065701-4.
Pallett, R.J. and Lark, R.J., 2001, "The use of tailored blanks in the manufacture of constuction components", Journal of Materials Processing Technology, Vol. 117, pp. 249-254.
Piwonka, T.S. and Flemings M.C., 1966, "Pore formation during solidification", Transactions of Metallurgical Society AIME, Vol. 236, pp. 1157-1165.
Rappaz, M. et al, 1999, "A new hot tearing criterion", Metallurgical and Materials Transactions, Vol. 30A, pp. 449-455.
Rotzer I., 2005, "Laser-beam welding maker aircraft lightef', Fraunhofer Magazine, Vol. 1, pp. 36-37.
Siqueira, R.H.M. et al, 2012, "Microstructural and Mechanical Characterization of Laser Welded and Heat-Treated AA6013 Aluminum Alloy", In: Proceedings of XI Brazilian MRS Meeting, CD-Rom.
ThermoCalc thermodynamic database, 1994, version J, Stockholm Royal Institute, Sweden.
Wikipedia, the free encyclopedia, 2012, Von Mises yield criterion, Retrieved in June 25, 2012, from http://en.wikipedia.org/wiki/Von_Mises_yield_criterion
» http://en.wikipedia.org/wiki/Von_Mises_yield_criterion

Publication Dates

Publication in this collection
Oct-Dec 2012

History

Received
11 July 2012
Accepted
04 Sept 2012

This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

[1] ASM - American Society of Materials, 1993, "Metals Handbook - Volume 6: Welding, Brazing, and Soldering", 10nd ed., Metals Park (Ohio), ASM International, pp. 1392-1393.

[2] Bordesoules, I. et al, 2007, "Trends in developments of Aluminium solutions for aerospace applications", In: Proceedings of the European Workshop on Short Distance Welding Concepts for Airframes frames - WEL-AIR, Hamburg, 13-15 june 2007, CD-Rom.

[3] Campbell, J., 2003, "Castings", 2nd ed., Oxford: Elsevier Pergamon, 332p.

[4] Clyne, T.W. and Davies G.J., 1975, "A Quantitive Solidification Test for Casting and An Evaluation of Cracking in Aluminium-Magnesium Alloys", The British Foundryman, Vol. 68, pp. 238-254.

[5] Drezet, J.M. et al, 2008, "Crack-free aluminium alloy welds using a twin laser process, In: 61st International Conference of the International Institute of Welding", Graz. Safety and reliability of welded components in energy and processing industry. Graz (Áustria), TU-Graz, pp. 87-94.

[6] Duarte, I. and Banhart, J., 2000, "A study of aluminium foam formation-kinetics and microstructure", Acta Materialia, Vol. 48, pp. 2349-2362.

[7] King, D. et al, 2009, "Advanced aerospace materials: past, present and future, Aviation and The Environment", Vol. 3, pp. 22-27.

[8] Lima, M.S.F. et al, 2000, "Advanced laser welding process", European patent no. 01810986.8.

[9] Mangalgiri, P.D., 1999, "Composite materials for aerospace applications", Bulletin of Materials Science, Vol. 22, pp. 657-664.

[10] Page, A.J. and Sear, R.P., 2006, "Heterogeneous Nucleation in and out of Pores", Physical Review Letters, Vol. 97, pp. 065701-1-065701-4.

[11] Pallett, R.J. and Lark, R.J., 2001, "The use of tailored blanks in the manufacture of constuction components", Journal of Materials Processing Technology, Vol. 117, pp. 249-254.

[12] Piwonka, T.S. and Flemings M.C., 1966, "Pore formation during solidification", Transactions of Metallurgical Society AIME, Vol. 236, pp. 1157-1165.

[13] Rappaz, M. et al, 1999, "A new hot tearing criterion", Metallurgical and Materials Transactions, Vol. 30A, pp. 449-455.

[14] Rotzer I., 2005, "Laser-beam welding maker aircraft lightef', Fraunhofer Magazine, Vol. 1, pp. 36-37.

[15] Siqueira, R.H.M. et al, 2012, "Microstructural and Mechanical Characterization of Laser Welded and Heat-Treated AA6013 Aluminum Alloy", In: Proceedings of XI Brazilian MRS Meeting, CD-Rom.

[16] ThermoCalc thermodynamic database, 1994, version J, Stockholm Royal Institute, Sweden.

[17] Wikipedia, the free encyclopedia, 2012, Von Mises yield criterion, Retrieved in June 25, 2012, from http://en.wikipedia.org/wiki/Von_Mises_yield_criterion
» http://en.wikipedia.org/wiki/Von_Mises_yield_criterion

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