Milad Abiri - Master Student ،Sharif University of Technology
Mojtaba Movahedi - Department of Materials Science and Engineering ،Sharif University of Technology
Ahkan ozlati - Ph.D Student ،Sharif University of Technology

Aluminum and steel are the most utilized metals in industry and joining of these two has many applications including heat exchangers and parts in aluminum extraction process. In this research ،Upset Resistance Welding of aluminum to stainless steels rods was studied. Macrostructure of the joints showed formation of upset at aluminum side of all samples. The upset size increased with welding heat input ،improving joints mechanical properties with removal of contaminations from weld interface. Microstructural studies from aluminum side of the samples exhibited recrystallization and grain growth (as a result of cold worked microstructure in base metal). At stainless steel side however ، formation of macro and micro twins was the dominant phenomena. A thin reaction layer (0.5 Micrometers) formed at the weld interface composed of intermetallic compounds ، and increasing heat input resulted in thickening (up to 2.3 Micrometers) and continuity of this layer. Microhardness test indicated hardness increase adjacent to weld interface in stainless steel side of the samples ،confirming formation of micro twins. Tensile strength of the samples increased with weld heat input (from ~67 up to ~84 MPa) ،but the formability and elongation of the welds were limited. Additionally ،post weld heat treatment resulted in enhancement of welds strength (up to two times) via promotion of the interdiffusion of the Al and Fe atoms through the joint interface.

Upset ResistanceWelding ،Aluminum AA6063 ،AISI304L stainless steel ،microstructure ،mechanical properties.