reported the joint strength between304 stainless steel and Al 6013-T4 with thickness of 4 mm canreach approximately 70% of the base aluminum alloy. Ghoshet al. [10] did FSW of pure Al to 304 stainless steel and the ultimatetensile strength can achieve 82% of Al. Presence of Fe3Al was reported. Besides, equiaxed and finer grains exist in the stirring zone,which indicate the involved dynamic recrystallization process.Tanaka et al. [11] welded Al7075-T6 to mild steel of the thicknessof 3 mm. Tool rotational speed varies from 400 to 1200 rpm underthe welding speed of 100 mm/min. The highest tensile strengththey can achieve is 333 MPa, which is about 60% of the base aluminum alloy. Moreover, they reported an exponentially increasingrelation- ship between the interface strength and the reducingthickness of IMC layer, which has the composition of FeAl3. Leeet al. [12] did experiments on FW of Al6056-T4 to 304 stainlesssteel with thickness of 4 mm under the rotational speed of800 rpm and welding speed of 80 mm/min. The thin intermetalliccompound layer of 250 nm thickness was analyzed through transmission electron microscopy (TEM) and identified to be FeAl4. Chenand Kovacevic [13] joined Al6061 to AISI 1018 steel sheet with thethickness of 6 mm. Local melting of Aluminum was observed andshear-off steel platelets encompassed by IMC layers of Fe4Al13and Fe2Al5 existed in the weld nugget. Locally partial molten Aluminum was again reported by Jiang and Kovacevic [14] when theydid study on the same pair of materials with the same thickness.