Abstract:Rotary friction welding was conducted on A286 with a diameter of f25 mm under 300, 900 and 2100 rpm to understand the structural response of the joint welded at different rotation speeds. Joint morphologies, grain structures inside the morphologies and the corresponding mechanism that governs its formation were characterized and investigated using electron backscattered diffraction (EBSD), which focused on three featured zones located at the center, 1/2R and periphery of the joint. The influence of structural … Show more
“…TMAZ: Adjacent to the WZ is the TMAZ, where severe shear and plastic deformation occur [21,22]. There is a transition from equiaxed grains in the WZ to elongated grains in the TMAZ (Fig.…”
A defect-free Ti 2 AlNb joint has been obtained by the inertia friction welding (IFW) technology. The weld zone (WZ) is composed of B2 grains refined by discontinuous dynamic recrystallization and enhanced by grain refinement strengthening. And the average microhardness decreases by about 30 HV from the WZ to the base metal. In-situ SEM analysis reveals that the heterogeneous structure of the joint causes strong strain partitioning during tensile deformation. The microcrack initiation occurs at the interface of the initial B2 phases and B2/O boundaries. Owing to stress concentration, the multi-slip bands and cracks tend to generate in the heat-affected zone (HAZ), causing a premature fracture.
“…TMAZ: Adjacent to the WZ is the TMAZ, where severe shear and plastic deformation occur [21,22]. There is a transition from equiaxed grains in the WZ to elongated grains in the TMAZ (Fig.…”
A defect-free Ti 2 AlNb joint has been obtained by the inertia friction welding (IFW) technology. The weld zone (WZ) is composed of B2 grains refined by discontinuous dynamic recrystallization and enhanced by grain refinement strengthening. And the average microhardness decreases by about 30 HV from the WZ to the base metal. In-situ SEM analysis reveals that the heterogeneous structure of the joint causes strong strain partitioning during tensile deformation. The microcrack initiation occurs at the interface of the initial B2 phases and B2/O boundaries. Owing to stress concentration, the multi-slip bands and cracks tend to generate in the heat-affected zone (HAZ), causing a premature fracture.
“…[18,19]. CDFW has successfully welded numerous kinds of materials (e.g., various steels [20,21], aluminum alloys [22], titanium alloys [23], nickel-based superalloys [24], etc.). These studies concentrate on the influence of CDFW process parameters on the microstructure and mechanical properties of the as-welded joints.…”
In the present paper, the continuous-drive friction welding (CDFW) technology has been successfully applied to join the U75V rail steel. The base metal (BM) of U75V rail steel is lamellar pearlite, and the weld zone could be clearly divided into three subzones (i.e., heat affected zone, thermo-mechanical affected zone (TMAZ), and central weld zone (CWZ)). Electron back-scattered diffraction examinations revealed the martensitic evolution in TMAZ and CWZ, suggesting that the experienced high temperature, severe plastic deformation, and fast cooling rate induce the microstructure transition during the CDFW process. The hard and brittle martensite structure explains the raised microhardness profiles and the reduced impact absorption energy of the as-welded joints. The CDFW process parameters govern the joint properties via influencing the welding heat input and plastic deformation by spindle speed and friction pressure at the friction stage, and the plastic deformation layer (flash) extrusion by upsetting pressure at the upsetting stage. More favorable results could be obtained at small set values of spindle speed (1800 rpm) and friction pressure (75 MPa) with less heat input and plastic deformation, and a large set value of upsetting pressure (175 MPa) with more flash extrusion, whose tensile strength reached 94.3% of that of the BM.
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