Jeong-Won Choi 교수

The interfacial temperature, microstructure and hardness distribution of the linear friction welded Ti-6Al-4V joints obtained at different applied pressures were investigated. The sound Ti-6Al-4V alloy joints were successfully fabricated below the β-phase transformation temperature. The increased pressure considerably decreased the welding temperature. The dynamically recrystallized ultra-fined α equiaxed grains of 0.2 μm were formed in the weld center of the joint by applying pressure of 550 MP

Dissimilar friction stir welding was conducted on the combination of pure Ti and carbon fibre reinforced plastic. The weld interface microstructure and mechanical properties of the obtained joints were systematically investigated. Before welding, a surface treatment was performed on the Ti surface using a silane coupling agent. As a result, the silane coupling agent treatment helped to fabricate the sound dissimilar Ti/CFRP joint. The dissimilar Ti/CFRP joints obtained at the interface temperatu

Linear friction welding (LFW) of Ti-6Al-4V alloy at various applied pressures and frequencies was performed. The influence of the applied pressure and frequency on the interfacial microstructure and mechanical properties of the joint was systematically investigated. The peak interfacial temperature was dominated by the applied pressure, while there is no significant variation in the peak interfacial temperature by the frequency. At low applied pressure, α-lamella structure formed inside the recr

It is known that one of the main concerns associated with the conventional welding of precipitation-strengthened Al alloys is the formation of softening regions, resulting in the deterioration of mechanical properties. In this study, we show that linear friction welding (LFW) can completely suppress softening regions in precipitation-strengthened AA6061-T6 alloy by introducing a large shear strain and by controlling the interfacial temperature. We found that the LFW process resulted in an extrem

Linear friction welding (LFW) of AA1050 and AA5052 was performed at various applied pressures. The strengthening contributions of the joints were examined to investigate the relationship between the microstructure and mechanical properties. The dominant strengthening mechanisms at the weld centre of the AA1050 joint were both the grain-boundary strengthening and dislocation strengthening. While the weld centre in the AA5052 joint was dominated by the grain-boundary strengthening since the dynami

The microstructure evolution of the AA5052-H34 joint and AA5083-O joint fabricated by linear friction welding (LFW) was evaluated in a wide range of interfacial temperatures, i.e., applied pressures. The grain refinement of Al alloys with high stacking fault energy was found to be mainly dominated by discontinuous dynamic recrystallization (DDRX) at low temperatures. While, it was clear that grain refinement at high temperatures was dominated by continuous dynamic recrystallization (CDRX). In th

Linear friction welding (LFW) was performed on face-centered cubic materials, that is, Al alloys (AA1050 and AA5052) with different stacking fault energies (SFEs). The pressure was controlled during the LFW to clarify the effects of temperature, strain, and strain rate on microstructural evolution and dynamic recrystallization (DRX) mechanism. The microstructural evolution during DRX was mainly dependent on the temperature. The grain structures and textural evolution at high temperatures were go

Dissimilar linear friction welding (LFW) of AA5052/AA6061 was performed at different applied pressures. A dissimilar joint obtained at a high applied pressure of 200 MPa exhibited a tensile strength equivalent to that of the AA5052 base material, mainly because of the high density of low-angle grain boundaries (LAGB) per unit area at the weld regions. Meanwhile, the joints obtained at low applied pressures of 30 and 100 MPa softened at the weld regions because the LAGB density decreased because