Microstructure and Mechanical Properties of Cold Metal Transfer Welding Similar and Dissimilar Aluminum Alloys

doi:10.1007/s40195-015-0252-6

Abstract

Abstract:

Integrating structures made from aluminum alloys in automotive industry requires a large amount of joining. As a consequence, the properties of the joints have a significant influence on the overall performance of the whole structure. Robot cold metal transfer welding is a relatively new joining technique and has been used in this work to join 6082-T4 and 5182-O aluminum alloy sheets by using ER5356 and ER4043 filler metals. Microstructure characterization was performed by optical microscopy and energy dispersive X-ray spectroscopy, and the mechanical properties were measured by tensile and hardness tests. A correlation is made between welding variables, mechanical properties and the microstructure of welded joints. Results indicate that robot cold metal transfer welding provides good joint efficiency with high welding speed, good tensile strength, and ductility. Owing to the low heat input of robot cold metal transfer welding process, the heat affected zone microstructure was quite similar to base metals, and weld metal microstructure was the controlling factor of joint efficiency. The best performing were the 5182/5182 joints welded with ER5356 and these had mechanical property coefficients of 100%, 98%, and 85% for yield strength, ultimate tensile strength, and elongation, respectively.

Key words: Aluminum, CMT, Welding, Microstructure, Tensile, property

Ahmed Elrefaey, Nigel G. Ross. Microstructure and Mechanical Properties of Cold Metal Transfer Welding Similar and Dissimilar Aluminum Alloys[J]. Acta Metallurgica Sinica (English Letters), 2015, 28(6): 715-724.

Figures/Tables 12

Table 1 Chemical composition (wt%) of the aluminum alloys and filler metals

Material	Si	Fe	Cu	Mn	Mg	Cr	Zn	Ti	Others	Al
6082-T4	0.7-1.3	0.5	0.1	0.4-1.0	0.6-1.2	0.25	0.2	0.1	0.15	Bal.
5182-O	0.2	0.35	0.15	0.2-0.5	4.0-5.0	0.1	0.25	0.1	0.15	Bal.
ER5356	0.25	0.4	0.1	0.05	4.5	0.05	0.1	0.06	0.06	Bal.
ER4043	5.6	0.8	0.3	0.05	0.05	0.05	0.1	0.02	0.08	Bal.

Table 2 Welding parameters

Filler	Base metal combinations	No.	Current (A)	Voltage (V)	Welding speed (mm/s)	Wire feed rate (m/min)	Heat input (kJ/mm)
ER5356	6082/6082	1	69	14.3	10	4.3	0.089
		2	93	15.1	15	5.5	0.084
		3	104	15.4	20	6.2	0.072
	6082/5182	4	69	15.7	10	4.3	0.098
		5	93	14.9	15	5.5	0.083
		6	104	16.2	20	5.7	0.076
	5182/5182	7	69	13.9	10	4.3	0.086
		8	93	14.9	15	5.5	0.083
		9	96	15.0	20	5.7	0.065
ER4043	6082/6082	10	55	15.1	10	2.9	0.075
		11	82	15.5	15	3.4	0.076
		12	90	16.6	20	3.7	0.067
	6082/5182	13	55	14.9	10	2.9	0.074
		14	82	16.1	15	3.4	0.079
		15	90	16.7	20	3.7	0.068
	5182/5182	16	55	15.8	10	2.9	0.078
		17	78	16.7	15	3.2	0.078
		18	86	16.4	20	3.5	0.065

Fig. 1 Robot head and sample clamping before welding

Fig. 2 Schematic view of the welded joint showing the locations of test samples (unit: mm)

Fig. 3 Polarized (bottom) and unpolarized (top) light images showing the microstructure of the base metals: a 6082 alloy; b 5182 alloy

Fig. 4 Bead profiles and cross-sectional macrostructures of representative joints: a, b, c sample No. 1; d, e, f sample No. 3; g, h, i sample No. 10; j, k, l sample No. 12

Fig. 5 Typical microstructures of the dissimilar joints No. 6 a, No. 15 e, polarized (bottom) and unpolarized (top) optical light images showing the microstructures of the WM of joints No. 6 b, No. 15 f, 5182 HAZ/WM interface of joints No. 6 c, No. 15 g 6082 HAZ/WM interface of joints No. 6 d, No. 15 h

Fig. 6 SEM images showing the microstructure of sample No. 6: a WM; b WM/6082 HAZ; c WM/5182HAZ

Fig. 7 SEM image a, EDS spectrum of the weld metal area b, EDX maps of elements in the weld metal of sample No. 6 c-f

Fig. 8 Micro-hardness profiles across the welded joints produced under different welding parameters, the 0 mm position is taken as the left-most edge of the weld metal: a samples No. 1 and No.3; b samples No.10 and No. 12; c samples No. 4 and No. 6; d samples No.13 and No.15; e samples No. 7 and No. 9; f samples No.16 and No.18

Fig. 9 Mechanical properties of different weld joints made with ER5356 a, ER4043 b filler metals

Table 3 Properties of the aluminum substrates at room temperature

Material	Tensile strength (MPa)	Yield strength (MPa)	Elongation (%)
6082-T4	296	180	28.3
5182-O	297	143	24.1

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