Comparative experimental study on the modification of microstructural and mechanical properties of friction stir welded and gas metal arc welded EN AW‐6061 O aluminum alloys by post‐weld heat treatment

Abstract

In this paper, the effects of post‐weld heat treatment on modification of microstructures and mechanical properties of friction stir welded and gas metal arc welded AA6061‐O plates were compared with each other. Gas metal arc welding and friction stir welding were used as the applicable welding processes for AA6061‐O alloys. The applied post‐weld heat treatment consisted of solution heat treatment, followed by water quenching and finally artificial aging. The samples were classified as post‐weld heat treated and as‐welded joints. The microstructural evolution, tensile properties, hardness features and fracture surfaces of both as‐welded and post‐weld heat treated samples were reported. The results clearly showed that friction stir welding process demonstrated better and more consistent mechanical properties by comparison with the gas metal arc welding process. The weld region of as‐welded samples exhibited a higher hardness value of 80 HV0.1 compared to the base material. In addition, the feasibility of post‐weld heat treatment in order to enhance the mechanical properties and to obtain more homogeneous microstructure of 6061‐O aluminum alloys was evaluated.

Influence of process parameters on the mechanical properties and corrosion resistance of dissimilar friction stir welded joints of AA2024-O and AA6061-O aluminum alloys

“…In general, for evaluated conditions, the behavior of microhardness profiles shows an increase in the welded joints regions due to annealed condition of the base metals and solid-state deformation effects produced by the FSW process. The base metals displayed average microhardness values of 42 HV for AA6061-O and 56 HV for AA2024-O, which are consistent with the results reported in other works [41,43]. The highest microhardness value (131HV) was obtained in HH-condition welded joints and is located nearly to ZATM of the advancing side (2024-O).…”

“…All fracture regions were located on the AA-6061-O side. For the HH condition, it is probable that the homogenization of the microstructure of both materials in the stir region increased the quantity of AA2024-O in the mixture, slightly increasing the tensile properties of the welded joint compared to the LL conditions [41,43]. Although the probable highest density of dislocations produced by the light-high ratio (ω/v) of LL conditions compared to HH condition could explain the apparent higher observed yield strength in this welded joint [43].…”

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

“…They came to the expected conclusion that better mechanical and fatigue properties were obtained with the FSW method. A similar comparison was also made by Gencer et al [5] and Jannet et al [6], with a similar result to that found by Kuleci.…”

“…Wang [7] was able to increase the mechanical properties of welded joints from an initial value of 69% up to 84% of the base material after applying the heat treatment. The UTS value of the joint was 284 MPa and Gencer [5] achieved a joint strength of 83% of the base material after applying T6 heat treatment using the FSW method.…”

“…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.…”