The post welding corrosion behaviour of aluminium 7004 alloy is investigated. The corrosion behaviour is compared among the specimens welded together by various techniques such as Friction Stir Welding (FSW), Tungsten Inert Gas welding (TIG), and Metal Inert Gas welding (MIG).

TIG and MIG welding were done using a suitable filler metal, and FSW was without filler metal. FSW was carried out at rotational speed of 320 and 960 rpm, and tool travel speed of 0.5, 1, 1.5 mm/s. The average grain size of TIG and MIG samples were observed as 70±5 μm and 75±5 μm respectively, whereas FSW samples resulted in average grain size ranging from 6 to 22±2 μm.

Fine grains with an average size of 6±2 μm were observed in the sample with a low rotational speed of 320 rpm and tool travel speed of 0.5 mm/s. The hardness of TIG sample at nugget zone was 67 HV, whereas MIG sample at nugget zone was 78 HV.

All samples of FSW show hardness value in the range of 108 to 120 HV. Corrosion test shows that corrosion rate of TIG sample was 12.63 × 10⁻³ mm/yr and the same that of MIG sample was 7.16 × 10⁻³ mm/yr. The corrosion rate of BM was found to be 1.88 × 10⁻³ mm/yr, whereas FSW with 320 rpm at 0.5 mm/s was 0.042 × 10⁻³ mm/yr, indicating that the FSW joints show better corrosion resistance among all the welded joints including BM.

This article is shared by Akhtar Kureshi, Sudeep Kumar T., Ayush Sourav, Sushil Yebaji, T. Shanmugasundaram