Experimental study on the strength of Fe-SMA to Q355 structural steel butt welded joints

Iron-based shape memory alloy (Fe-SMA) is a high-performance alloy known for its excellent low-cycle fatigue resistance, making it highly suitable for metal damping technologies. By integrating Fe-SMA with cost-effective normal strength structural steel, such as Q355 with a nominal yield strength of 355 MPa, through welding, the amount of Fe-SMA required in a damper can be reduced, thus improving the economic feasibility of Fe-SMA-based damping systems. The study begins with examining the effect of different weld fillers on the mechanical properties of Fe-SMA to Fe-SMA butt joints, finding both carbon steel weld wire JL-J50 and stainless steel weld wire ER316L had good fusion with the Fe-SMA base metal. Since the carbon steel weld wire is less expensive and the corresponding butt joints had only slightly lower ultimate capacity than those adopting stainless steel weld wire, the weld wire JL-J50 was considered as a cost-effective selection. Then, an experimental study on the butt welding of Fe-SMA to Q355 structural steel plates using tungsten inert gas arc welding and carbon dioxide shielded welding techniques was carried out. The weld filler, carbon steel, and stainless steel welding wires were adopted in the dissimilar welded joints of Fe-SMA to Q355 by the tungsten inert gas arc welding method. The welded joints underwent microstructure observation tests, micro shear test, hardness test, DIC full-field strain measurements, and tensile tests. The results indicate that TIG welded joints adopting carbon steel weld wire JL-J50 exhibited excellent ductility, with ductile failure occurring in the Q355 base material, while joints adopting carbon dioxide shielded welding show brittle failure at the fusion line. © 2024 Elsevier Ltd