Residual stress and plastic strain in AI51 304L stainless steel/titanium friction welds

Abstract

Detailed finite element modelling is employed to elucidate the residual stress and plastic strain produced during dissimilar friction welding of AISI 304L stainless steel and titanium substrates. Heat transfers into a narrow zone (± 20 mm either side of the bondline) as a result of the friction welding operation. Since titanium has a lower thermal conductivity than AISI 304L stainless steel, higher peak temperatures are attained in AISI 304L stainless steel material in the region adjacent to the bondline. Close to the bondline, the radial component of the residual stress σr is tensile in the substrate with the higher thermal expansion coefficient (AISI 304L stainless steel), and compressive in the substrate with the lower thermal expansion coefficient (titanium). At the periphery of the welded component, the axial residual stress component σz is compressive in the AISI 304L stainless steel near the bondline, and tensile in regions far from the bondline. In titanium at the component periphery, σz is tensile, except in the region extremely close to the bondline. At the centre of the component, σz is tensile near the bondline and compressivefar from the bondline in both substrates. Considerable plastic strain is produced perpendicular to the bondline and in the radial direction. In particular, the titanium substrate immediately adjacent to the bondline is severely strained. Limited plastic straining occurs in the circumferential direction.MST/2085