Fabrication Commercial Pure Titanium-304 Stainless Steel Bimetal with Impressive Mechanical Properties

During friction stir welding-based cladding, the movement of the welding tool on the surface of the clad layer always requires machining and polishing after establishing the joining, leading to material loss and increased manufacturing time of the bimetal. Also, stirring in the interface can result in unwanted metallurgical transformation. In this research, Ti-SS304 bimetal was fabricated using friction stir welding-based cladding. The problems were fixed using a small pin and performing a process with a low traverse speed on the SS304 substrate layer. The results showed that Ti and SS304 steel layers are mechanically locked together as the traverse speed decreases at the interface. Also, the average grain size of the stir zone increases from 0.8 ± 0.3 to 3.8 ± 0.9 μm by decreasing the traverse speed from 20 to 5 mm/min. The necklace structure appears in the stir zone by increasing the traverse speed by 20 mm/min. Under the influence of plastic deformation during the process, static recrystallization during cooling leads to the formation of an equiaxed grain microstructure on the upper surface of the titanium sheet. The maximum values of yield and ultimate tensile strength relate to the bimetal fabricated at the traverse speed of 10 mm/min and rotational speed of 1000 rpm, which are 161 and 53% higher than the SS304 base metal, respectively, and 174 and 176% higher than the commercially pure Ti (base metal), respectively. As the traverse speed increases, the corrosion resistance in simulated body fluid (SBF) decreases.