Microstructure and Mechanical Properties of Friction Stir Welded Austenitic-Ferritic Stainless Steels Using Staggered Joint Configuration

Dissimilar friction stir welding of 304 austenitic stainless steel and 430 ferritic stainless steel was performed by using staggered butt joint configuration. Under proper heat input, welding experiments were carried out to study the effect of tooth dimension on material flow, microstructure evolution and mechanical properties of the joint. The results indicate that the material flow tends to improve with reduced the tooth width. However, when the tooth width is reduced to 1 mm, the mixing degree of base metals in stir zone becomes worse due to the lack of softened metal. It is noted that joint 2 with a tooth width of 2 mm is characterized by river pattern and shows various flow directions in different regions of the stir zone. This pattern is formed by the mixed structure of austenite and ferrite with various grain sizes. Joint 2 presents the maximum tensile strength in all specimens and failed in the ferritic base metal.