Comparative in Mechanical Behavior of 6061 Aluminum Alloy Welded by Pulsed GMAW with Different Filler Metals and Heat Treatments

Abstract

Precipitation hardening aluminum alloys are used in many industries due to their excellent mechanical properties, including good weldability. During a welding process, the tensile strength of the joint is critical to appropriately exploit the original properties of the material. The welding processes are still under study, and gas metal arc welding (GMAW) in pulsed metal-transfer configuration is one of the best choices to join these alloys. In this study, the welding of 6061 aluminum alloy by pulsed GMAW was performed under two heat treatment conditions and by using two filler metals, namely: ER 4043 (AlSi 5 ) and ER 4553 (AlMg 5 Cr). A solubilization heat treatment T4 was used to dissolve the precipitates of β"phase into the aluminum matrix from the original T6 heat treatment, leading in the formation of β-phase precipitates instead, which contributes to higher mechanical resistance. As a result, the T4 heat treatment improves the quality of the weld joint and increases the tensile strength in comparison to the T6 condition. The filler metal also plays an important role, and our results indicate that the use of ER 4043 produces stronger joints than ER 4553, but only under specific processing conditions, which include a moderate heat net flux. The latter is explained because Mg, Si and Cu are reported as precursors of the production of β"phase due to heat input from the welding process and the redistribution of both: β" and β precipitates, causes a ductile intergranular fracture near the heat affected zone of the weld joint.

Influence of Preheating Temperature on Changes in Properties in the HAZ during Multipass MIG Welding of Alloy AW 6061 and Possibilities of Their Restoration

“…Cold-joint-type defects (see Figure 4) occur throughout the weld length and in all weld beads. However, similar defects also occur when welding lower thicknesses without preheating, as proven by Guzman et al [8] on 7-mm-thick plates. Materials of lower thicknesses can then be welded using various methods without preheating, without causing cold joint defects.…”

“…Welding without preheating at smaller thicknesses resulted in decreased hardness varying from 65 to 73 HV with an HAZ width of 6 mm [8], 70 HV for a width of 6 mm [9], 61-68 HV for an HAZ width of 7 mm [7] and 66 HV for an HAZ width of 14 mm [3]. From these results, it is clear that the effect of welding with preheating has a similar effect on the hardness decrease in HAZ as welding without preheating.…”

“…Authors such as Guzman et al [8], Peng et al [9], Hilty [10], Wang et al [7] and Gencer et al [5], in addition to assessing the effects of degradation on the mechanical properties during welding, have also dealt with the possibility of restoring the mechanical properties of welded joints via heat treatment. Guzman [8] assessed the mechanical properties of welded joints made by MIG welding with two types of filler materials (ER 4043 and ER 5356) and with subsequent heat treatment under T4 and T6 conditions. The best results were obtained after welding with the filler material ER 4043, whereby ultimate tensile strength (UTS) values of 153 MPa were achieved identically after both T4 and T6 heat treatment.…”

Weld Geometry, Mechanical Properties, Microstructure and Chemical Composition of AA6063 in Tungsten Inert Gas Welding with Intermittent Controlled Wire Feeding Method

“…Aluminum AA6063 with a thickness of 3 mm and ER-5356 (AlMg5Cr) [26] with a diameter of 1.2 mm were used as base metal and filler metal. The specimen was cut into 120 mm × 50 mm × 3 mm, and a butt joint configuration was prepared for the GTAW using Miller Dynasty 210 DX TIG Welding machine (Miller Electric Mfg.…”

“…The difference in UTS results occurs because the heat input is fixed, but the amount of filler metal is different so that at a large ratio, the penetration of the aluminum alloy is reduced, resulting in a lower temperature [26]. Low temperature results in increased tensile strength, but the amount of filler in each ratio is quite different.…”