Tensile strength and microstructure of laser welding of AZ31 magnesium alloy thick plates

TANG Hai-guo; GAO Ming; ZENG Xiao-yan

doi:10.3969/j.issn.1001-3806.2011.02.003

To deepen the understanding of laser welding of magnesium alloys,a high power CO2 laser was employed to join AZ31 magnesium alloy in 10mm thick.Its microstructure and tensile strength of laser welds were studied.Obvious concaves appeared on the welding surface because of serous burning-lost of magnesium at high temperature.Under the experimental conditions,the microstructure of the welding zone was equiaxed dendrites and the grains were refined with the decrease of the welding heat.The tensile test results showed surface concaves and porosities were two main factors affecting the tensile strength. The maximum tensile strength was only 74% of the substrate metal if the surface including concaves.However,it reached 91% of the substrate metal after surface concaves were eliminated by laser repair welding.Besides,the porosities were the main affecting factor inducing the tensile strength of laser repair weld is lower than that of the substrate metal.The results show it is necessary to eliminate the surface concaves and weld porosities in order to increase the mechanical property of laser welding joints.

Tensile strength and microstructure of laser welding of AZ31 magnesium alloy thick plates

Corresponding author: GAO Ming, mgao@mail.hust.edu.cn;

1. Wuhan National Laboratory for Optoelectronics, School of Optoelectronics Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

Received Date: 2010-05-25

Accepted Date: 2010-07-19

Available Online: 2011-03-25

Abstract: To deepen the understanding of laser welding of magnesium alloys,a high power CO2 laser was employed to join AZ31 magnesium alloy in 10mm thick.Its microstructure and tensile strength of laser welds were studied.Obvious concaves appeared on the welding surface because of serous burning-lost of magnesium at high temperature.Under the experimental conditions,the microstructure of the welding zone was equiaxed dendrites and the grains were refined with the decrease of the welding heat.The tensile test results showed surface concaves and porosities were two main factors affecting the tensile strength. The maximum tensile strength was only 74% of the substrate metal if the surface including concaves.However,it reached 91% of the substrate metal after surface concaves were eliminated by laser repair welding.Besides,the porosities were the main affecting factor inducing the tensile strength of laser repair weld is lower than that of the substrate metal.The results show it is necessary to eliminate the surface concaves and weld porosities in order to increase the mechanical property of laser welding joints.

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Reference (18)

[1]	FRIEDRICH H E,MORDIKE B L.Magnesium technology[M].Berlin:Springer,2006:63-107.
[2]	CHEN Z H,YAN H G,CHEN J H,et al.Magensium alloys[M].Beijing:Chemical Industry Press,2004:1-25(in Chinese).
[3]	LIU L M,WANG J F,SONG G.Hybrid laser-TIG welding,laser beam welding and gas tungsten arc welding of AZ31B magnesium alloy[J].Materials Science and Engineering,2004,A381(1/2):129-133.
[4]	WOHLFAHRT H,RETHMEIER M,BOUAIFI B,et al.Metal-inert gas welding of magnesium alloy[J].Welding and Cutting,2003,55(2):80-84.
[5]	XING L,KE L M,SUN D C,et al.Friction-stir eelding of MB8 magnesium alloy sheet[J].Transactions of the China Welding Institution,2006,22(6):18-21 (in Chinese).
[6]	CHI C T,CHAO C G,LIU T F,et al.A study of weldability and fracture modes in electron beam weldments of AZ series magnesium alloys[J].Materials Science and Engineering,2006,A435/436:672-680.
[7]	SUN Z,PAN D,WEI J.Comparative evaluation of tungsten inert gas and laser welding of AZ31 magnesium alloy[J].Science and Technology of Welding and Joining,2002,7 (6):343-351.
[8]	LIU L M,WANG J F,SONG G.Hybrid laser-arc welding of AZ31B Mg alloy[J].Chinese Journal of Lasers,2004,31 (2):1523-1526(in Chinese).
[9]	FENG J C,WANG Y R,ZHANG Z D.Status and expectatiou of research on welding of magnesium alloy[J].The Chinese Journal of Nonferrous Metals,2005,15 (2):165-178 (in Chinese).
[10]	KANNAN M B,DIETZEL W,BLAWERT C,et al.Stress corrosion cracking behavior of Nd:YAG laser butt welded AZ31 Mg sheet[J].Materials Science and Engineering,2007,A444(1/2):220-226.
[11]	QUAN Y J,CHEN Z H,YU Z H,et al.Microstructure and properties of joints of wrought magnesium alloy AM60 plates welded by laser beam welding[J].The Chinese Journal of Nonferrous Metals,2007,17(4):525-529(in Chinese).
[12]	QUAN Y J,CHEN Z H,GONG X S,et al.CO2 laser beam welding of dissimilar magnesium-based alloys[J].Materials Science and Enginecring,2008,A496(1/2):45-51.
[13]	WU Q,XU L Y,CHEN G Y,et al.Experimental study about CO2 laser welding of galvanized sheet[J].Laser Technology,2007,31(6):571-574(in Chinese).
[14]	CAO X,JAHAZI M,IMMARIGEON J P,et al.A review of laser welding techniques for magnesium alloys[J].Journal of Materials Processing Technology,2006,171 (2):188-204.
[15]	WU Q,XU L Y,CHEN G Y,et al.Corrosion property of the laser welded joint of high-strength galvanized sheet[J].Laser Technology,2008,32(3):334-337(in Chinese).
[16]	YUYC,WANG C M,DENG Y P,et al.Microstructure and properties of YAG-MIG hybrid welding joint of ZL-114A aluminum alloy[J].laser Technology,2008,32(6):601-604(in Chinese).
[17]	ZHAO H,DEBROR T.Pore formation during laser beam welding of diecast magnesium alloy AM60OB-mechanism and remedy[J].Welding Journal,2001,80(8):204-210.
[18]	PASTOR M,ZHAO H,DEBROY T.Continuous wave Nd:yttriumaluminium-garnet laser welding of AM60B magnesium alloys[J].Journal of Laser Applicatiou,2000,12(3):91-100.

Tensile strength and microstructure of laser welding of AZ31 magnesium alloy thick plates

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