Geometrical and microstructural characteristics of the TIG-CMT hybrid welding in 6061 aluminum alloy cladding

Profile Map of Weld Beads and Its Formation Mechanism in Gas Metal Arc Welding

“…Hence, as shown by the green lines in Figure 2a, the typical profile characteristic in this stage is the excess within the maximum width of deposited filler metal on the base metal over that of the weld pool. Furthermore, under the combined effect of poor wettability resulting from a small welding current [12] and surface tension, a smaller contact angle of 114.5 • will be formed after the molten wire spreads and accumulates on the surface of the base metal, as represented by Figure 2f,g. The smaller the welding current, the greater the volume deviation of the melted wire over the melted base metal, and thus the greater volume of the overflowing melted wire, which leads to a greater width deviation between the reinforcement and the weld pool.…”

“…An example for this viewpoint is the bead welded by cold metal transfer (CMT) + pulse process [7], which is characterized by a significant width deviation: The maximum width of reinforcement is 219% of that of the weld pool and the contact angle is only 26.8 degrees, as can be seen from Figure 2h. Another example is the bead welded by tungsten inert gas welding (TIG) + CMT hybrid welding [12] in which the maximum width of reinforcement is also double that of the weld pool and the contact angle is nearly 90 • . Figure 2 shows the map of weld beads, which displays clearly that with the increase of mean current, the profile can be divided into three stages according to the volume relationship between the melted filler metal and the weld pool: the melted filler metal (i) overflowing (Figure 2a), (ii) matching ( Figure 2b-d), and (iii) inadequate (Figure 2e) for the weld pool when the average current is at a low, medium, and high level, respectively.…”

“…An example for this viewpoint is the bead welded by cold metal transfer (CMT) + pulse process [7], which is characterized by a significant width deviation: The maximum width of reinforcement is 219% of that of the weld pool and the contact angle is only 26.8 degrees, as can be seen from Figure 2h. Another example is the bead welded by tungsten inert gas welding (TIG) + CMT hybrid welding [12] in which the maximum width of reinforcement is also double that of the weld pool and the contact angle is nearly 90°. The width difference between reinforcement and weld pool decreases gradually with increasing average current and finally diminishes when the current is up to 120 A.…”

“…The decreased volume difference makes most of the melted filler wire held by the growing weld pool, thus leaving less melted filler wire overflowing the weld pool. Hence, less melted filler wire spreads and [7], with permission of Elsevier, 2016); and (i) bead of TIG-CMT (reproduced from [12], with permission of Elsevier, 2017).…”

“…Profiles of weld bead and its dimensions. (a) 72 A; (b) 88 A; (c) 104 A; (d) 120 A; (e) 136 A; (f) schematic of measurement; (g) contact angle; (h) bead of CMT + P (reproduced from[7], with permission of Elsevier, 2016); and (i) bead of TIG-CMT (reproduced from[12], with permission of Elsevier, 2017).…”