Microscopic Structure and Property of Double-Electrode Gas Metal Arc Welding of AZ31B Magnesium Alloy

doi:10.1007/s12204-017-1834-4

Abstract

Abstract: This paper focuses on the research on double-electrode gas metal arc welding (DE-GMAW) of AZ31B magnesium alloy sheet with 2mm thickness. During the welding process, stable hybrid arc of metal inert gas (MIG) and tungsten inert gas (TIG) is employed as welding heat source. Optical and electron microscopes are used to observe the microstructures of the weld joint. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) are employed to identify the components in fusion zone. Microhardness is also tested. When the MIG current is 80A, the perfect weld joint is obtained, though figures of fish scales are observed in all joints in the research. The fusion zone is formed by dendrites, where β-Mg17(Al, Zn)12 is dispersed. The hardness in fusion zone and heat affected zone (HAZ) is lower than that in base metal (BM). The average Vickers hardness of fusion zone and HAZ is about 58 and 56 respectively, while the Vickers hardness of BM is about 63.

Key words: double-electrode gas metal arc welding (DE-GMAW)| dendrite| eutectic reaction| AZ31B magnesium alloy

摘要： This paper focuses on the research on double-electrode gas metal arc welding (DE-GMAW) of AZ31B magnesium alloy sheet with 2mm thickness. During the welding process, stable hybrid arc of metal inert gas (MIG) and tungsten inert gas (TIG) is employed as welding heat source. Optical and electron microscopes are used to observe the microstructures of the weld joint. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) are employed to identify the components in fusion zone. Microhardness is also tested. When the MIG current is 80A, the perfect weld joint is obtained, though figures of fish scales are observed in all joints in the research. The fusion zone is formed by dendrites, where β-Mg17(Al, Zn)12 is dispersed. The hardness in fusion zone and heat affected zone (HAZ) is lower than that in base metal (BM). The average Vickers hardness of fusion zone and HAZ is about 58 and 56 respectively, while the Vickers hardness of BM is about 63.

关键词: double-electrode gas metal arc welding (DE-GMAW)| dendrite| eutectic reaction| AZ31B magnesium alloy

CLC Number:

TG 444.2

MA Guohong1* (马国红), SHEN Xu1 (沈旭), PING Qiwen1 (平齐文),NIE Jun1 (聂军), YE Jia2 (叶佳). Microscopic Structure and Property of Double-Electrode Gas Metal Arc Welding of AZ31B Magnesium Alloy[J]. Journal of shanghai Jiaotong University (Science), 2017, 22(3): 286-290.

References 20

[1]	ZHANG Z D, LIU L M, SONG G. Welding characteristicsof AZ31B magnesium alloy using DC-PMIGwelding [J]. Transactions of Nonferrous Metals Societyof China, 2013, 23: 315-322.
[2]	HAFERKAMP H, NIEMEYERM, DILTHEY U, et al.Laser and electron beam welding of magnesium materials[J]. Welding and Cutting, 2000, 52: 178-180.
[3]	ZHANG Z D, LIU L M, SHEN Y, et al. Mechanicalproperties and microstructures of a magnesium alloygas tungsten arc welded with a cadmium chloride flux[J]. Materials Characterization, 2008, 59: 40-46.
[4]	WESTENGEN H. Magnesium die casting: From ingotsto automotive parts [J]. Light Metal Age, 2000,58: 44-52.
[5]	WAGNER D C, XIAO C, TANG X, et al. Liquationcracking in arc and friction-stir welding of Mg-Zn alloys[J]. Metallurgical and Materials Transactions A,2015, 46: 315-327.
[6]	WAHBA M, MIZUTANI M, KAWAHITO Y, et al.Laser welding of die-cast AZ91D magnesium alloy [J].Materials and Design, 2012, 33: 569-576.
[7]	PASTOR M, ZHAO H, DEBROY T. Continuouswave Nd: Yttrium-aluminum-garnet laser welding ofAM60B magnesium alloy [J]. Journal of Laser Applications,2000, 12: 91-100.
[8]	ZHAO H, DEBROY T. Pore formation during laserbeam welding of die-cast magnesium alloy AM60Bmechanismand remedy [J]. Welding Journal, 2001,80(8): 204-210.
[9]	LIU L M, ZHANG Z D, SONG G, et al. Mechanismand microstructure of oxide fluxes for gas tungsten arcwelding of magnesium alloy [J]. Metallurgical and MaterialsTransactions A, 2007, 38: 649-658.
[10]	YU Z H, YAN H G, CHEN S J, et al. Method for weldinghighly crack susceptible magnesium alloy ZK60 [J].Science and Technology of Welding and Joining, 2010,15(5): 354-360.
[11]	PADMANABAN G, BALASUBRAMANIAN V,SARIN SUNDAR J K. Influences of welding processeson microstructure, hardness and tensile propertiesof AZ31B magnesium alloy [J]. Journal of MaterialsEngineering and Performance, 2010, 19(2): 155-165.
[12]	MUNITZ A, COTLER C, STERN A, et al. Mechanicalproperties and microstructure of gas tungsten arcwelded magnesium AZ91D plates [J]. Materials Scienceand Engineering A, 2001, 302(1): 68-73.
[13]	WEN T, LIU S Y, CHEN S, et al. Influence of highfrequency vibration on microstructure and mechanicalproperties of TIG welding joints of AZ31 magnesiumalloy [J]. Transaction of Nonferrous Metals Society ofChina, 2015, 25(2): 397-404.
[14]	DAI J, HUANG J, WU Y X. Research on laser weldingof Mg-rare earth alloy Mg-3Nd-0.2Zn-0.4Zr [J]. Journalof Materials Engineering and Performance, 2012,21(2): 208-212.
[15]	LI C B, LIU L M. Investigation on weldability of magnesiumalloy thin sheet T-joints: Arc welding, laserwelding, and laser-arc hybrid welding [J]. InternationalJournal of Advanced Manufacturing Technology, 2013,65: 27-34.
[16]	YU S R, CHEN X J, HUANG Z Q, et al. Microstructureand mechanical properties of friction stir weldingof AZ31B magnesium alloy added with cerium [J].Journal of Rare Earth, 2010, 28(2): 316-320.
[17]	KANEMARU S, SASAKI T, SATO T, et al. Study forthe mechanism of TIG-MIG hybrid welding process [J].Weld World, 2015, 59: 261-268.
[18]	MA G H, ZHANG Y M. A novel DE-GMAW methodto weld steel tubes on simplified condition [J]. The InternationalJournal of Advanced Manufacturing Technology,2012, 63: 147-153.
[19]	SHI Y, WEN J X, XUE C, et al. Influence of NDEGMAWbypass current on weld penetration [J]. Journalof Lanzhou University of Technology, 2011, 37(1):17-20 (in Chinese).
[20]	NIE J. The research on weld forming of AZ31B magnesiumalloy in non-consumable double electrode GMAWprocess [D]. Nanchang: School of Mechanical Engineering,Nanchang University, 2015 (in Chinese).