Laser Beam Welding of Semi-Solid Rheocast Aluminium Alloy 2139

Abstract:

NASA developed aluminium alloy 2139 for use in airframe structural applications as the requirement for higher strength, corrosion resistant, aluminium alloys is increasing, however the need to weld ‘unweldable alloys’ is also becoming apparent. 2139 is seen to be in this class. Semi-solid rheocast aluminium plates (Al-Cu-Mg-Ag) were cast in high pressure die casts. In total 27 welds were fabricated in experimentation, 3 on each plate to avoid distortion by using a continuous wave Nd:YAG. The weldability of this Al-Cu alloy was assessed by optical microscopy to indicate the quality and geometry of the passes. Comparisons were made with As-Cast (F) tempers. Laser power parameters ranged from 3 kW to 4 kW and weld speeds from 4 m/min to 6 m/min. Welds were allowed to cool naturally. The results show that by varying speed and power, when combined with heat treatments, produce diverse results for this unweldable alloy.

• Periodical: Advanced Materials Research (Volume 1019)
• Pages: 81-89
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.1019.81
• Online since: October 2014
• Authors: C.R. Gilbert
• Keywords: AA2139 Aluminium Alloy, Al-Cu-Mg-Ag, Aluminium Alloy, Laser Beam Welding, Rheocast, Semi-Solid, Vickers Hardness

References

[1] M. C. Flemings, R. Mehrabian and R. G. Rick: US Patent No 3, 902, 544, (1975) September 2.

[2] Accessible on internet: http: /www. keytometals. com/Article12. htm.

[3] F. M. Ghaini et al.: The Relation Between Liquation and Solidification Cracks in Pulsed Laser Welding of 2024 Aluminium Alloy. Accessible on internet: http: /www. sciencedirect. com.

DOI: 10.1016/j.msea.2009.04.056

[4] M. Turna, P. Kovacocy: Zvaranie laserovym lucom. Bratislava, STU, 2003, ISBN 80-227-1921-8.

[5] H. Möller, G. Govender, The heat treatment of rheo-high pressure die cast Al-Cu-Mg-Ag alloy 2139, Solid State Phenomena Vols 192-193 (2013) pp.173-178.

DOI: 10.4028/www.scientific.net/ssp.192-193.173

[6] A. Cho, W. Barry Lisagor, T. T. Bales, Development and Processing Improvement of Aerospace Aluminium Alloys – Development of Al-Cu-Mg-Ag Alloy (2139) NASA/CR-2007-215094.

[7] D. Bakavos, P. B. Prangnell, B. Bes, F. Eberl, The effect of microstructural evolution in two 2xxx series Al-alloys with a high Cu: Mg ratio during ageing to a T8 temper, Materials Science and Engineering A 491 (2008) pp.214-223.

DOI: 10.1016/j.msea.2008.03.014

[8] K. Tsushima, K. Shibata, H. Sakamoto, Mechanical properties of aluminium die castings welded by Nd: YAG laser beams, Welding International, 19: 3, pp.193-198.

DOI: 10.1533/wint.2005.3399

[9] A. T. Kermandis, A. D. Zervaki, G. N. Haidemenopoulos, Sp. G. Pantelakis, Effects of temper condition and corrosion on the fatigue performance of a laser-welded Al-Cu-Mg-Ag (2139) alloy, Materials and Design 31 (2010), pp.42-49.

DOI: 10.1016/j.matdes.2009.07.020

[10] A. Garg, J. M. Howe, Grain boundary precipitation in an Al-4. 0Cu-0. 5Mg-0. 5Ag alloy, Acta Metall Mater 1992; 40: 2451-62.