Evolution of microstructure and crystallographic texture during dissimilar friction stir welding of duplex stainless steel to low carbon-manganese structural steel

Electron backscattered diffraction (EBSD) was used to analyze the evolution of microstructure and crystallographic texture during friction stir welding of dissimilar type 2205 duplex stainless steel (DSS) to type S275 low carbon-manganese structural steel. The results of microstructural analyses show that the temperature in the center of stirred zone reached temperatures between Ac 1 and Ac 3 during welding, resulting in a minor ferrite-to-austenite phase transformation in the S275 steel, and no changes in the fractions of ferrite and austenite in the DSS. Temperatures in the thermomechanically affected and shoulder-affected zones of both materials, in particular toward the root of the weld, did not exceed the Ac 1 of S275 steel. The shear generated by the friction between the material and the rotating probe occurred in austenitic/ferritic phase field of the S275 and DSS. In the former, the transformed austenite regions of the microstructure were transformed to acicular ferrite, on cooling, while the dual-phase austenitic/ferritic structure of the latter was retained. Studying the development of crystallographic textures with regard to shear flow lines generated by the probe tool showed the dominance of simple shear components across the whole weld in both materials. The ferrite texture in S275 steel was dominated by D 1, D 2, E, E¯ , and F, where the fraction of acicular ferrite formed on cooling showed a negligible deviation from the texture for the ideal shear texture components of bcc metals. The ferrite texture in DSS was dominated by D 1, D 2, I, I¯ , and F, and that of austenite was dominated by the A, A¯ , B, and B¯ of the ideal shear texture components for bcc and fcc metals, respectively. While D 1, D 2, and F components of the ideal shear texture are common between the ferrite in S275 steel and that of dual-phase DSS, the preferential partitioning of strain into the ferrite phase of DSS led to the development of I and I¯ components in DSS, as opposed to E and E¯ in the S275 steel. The formations of fine and ultrafine equiaxed grains were observed in different regions of both materials that are believed to be due to strain-induced continuous dynamic recrystallization (CDRX) in ferrite of both DSS and S275 steel, and discontinuous dynamic recrystallization (DDRX) in austenite phase of DSS

Electrochemical aspects and in vitro biocompatibility of Ti-SS304 layered composite

In the current research, in order to eliminate the release of toxic ions from the stainless steel 304 layer, a bi-layered Ti-SS304 biocomposite was made using the friction stir welding process, and the corrosion-cellular behavior of this biocomposite in simulated body fluid (SBF) was studied. The results show that the increasing temperature induced by increasing welding heat input during friction stir welding increases the thickness of the oxide layer formed on the titanium layer. By increasing the thickness of the oxide layer, the corrosion current density increases to 3.45 μA cm−2, the corrosion potential decreases to −0.24 V, and the corrosion rate increases to 0.029 mm/year. In addition, compared to samples fabricated with different traverse speeds of 5, 10, and 20 mm/min, the composite samples fabricated with different rotational speeds of 600, 800, and 1000 rpm did not show significant differences in corrosion current density due to competition effect of the titanium oxide layer and residual stress formed during friction stir welding by different rotational speeds. The two-layered Ti-SS304 composite fabricated at a rotation speed of 1000 rpm and a traverse speed of 20 mm/min shows the lowest corrosion current density and corrosion rate and the highest cell viability of 4.9 × 10 −7 A/cm−2, 4.26 × 10 −3 mm/year, and 92%, respectively

Effect of solution treatment of AZ91 alloy on microstructure, mechanical properties and corrosion behavior of friction stir back extruded AZ91/bioactive glass composite

In the present study, we investigated the effects of solution treatment and friction stir back extrusion on the microstructure, mechanical properties, and in-vitro corrosion behavior of the AZ91/64SiO2–31CaO–5P2O5 composite. The findings demonstrate that the reinforcing phase of bioactive glass in the AZ91 matrix exhibits a gradient distribution, resulting in grain refinement in the zone near the surface of the composite wire. The fabrication of the AZ91-3 vol% bioactive glass composite through friction stir back extrusion, utilizing a rotational speed of 1200 rpm and an extrusion speed of 20 mm/min, leads to a significant improvement in corrosion resistance compared to the solid solutionized AZ91 alloy, as demonstrated by a ∼93% increase in simulated body fluid (SBF). During the friction stir back extrusion of the solid solutionized AZ91 alloy, heat and plastic deformation result in the re-precipitation of the ß-Mg17Al12 phase in the α-Mg matrix. The presence of bioactive glass particles facilitates this re-precipitation process during friction stir back extrusion. In comparison to the solid solutionized AZ91 alloy, the AZ91-3 vol% bioactive glass composite exhibits a 23% increase in ultimate tensile strength (UTS), a 28% increase in yield strength (YS), and a 30% decrease in elongation

Effect of preprocessing heat treatment of the Al-16Si-4Cu alloy on microstructure and tribological behavior of friction-surfaced coating

This study investigated the simultaneous effect of the consumable rod's preprocessing heat treatment conditions (homogenization, solid solution, and artificial aging treatment) and severe plastic deformation on the properties of Al-Si-Cu alloy friction surfaced on a commercially pure aluminum alloy substrate. The friction-surfaced coating's microstructural evolution, mechanical properties, and wear resistance were evaluated. The results showed that coatings fabricated using artificially aging (T6)-treated consumable rods resulted in the highest coating width (17.02±0.83 mm) and maximum efficiency (39.78 ± 1.23 %). Friction surfacing using artificially aged and solid solution-treated consumable rods results in minimum (2.78 ± 0.28 µm) and maximum (6.32±0.34 µm) coating grain sizes, respectively. Friction surfacing using T6-treated consumable rods results in smaller, more uniformly distributed Si particles in the coating microstructure. Compared to the other consumable rods, the coatings fabricated using T6-treated consumable rods result in the highest hardness (110.54±10.29 HV0.1), maximum bond strength (14.15±0.75 kN), and lowest wear rate (0.20±0.03 µg/Nm)

Effect of SiC nanoparticles on the microstructure and texture of friction stir welded AA2024/AA6061

Babol Noshirvani University of Technolog