A combination of extrusion and equal channel angular pressing （ECAP） was used to deform a plain low carbon steel. This process consists of two successive deformations by extrusion and ECAP in a single die （Ex-ECAP...A combination of extrusion and equal channel angular pressing （ECAP） was used to deform a plain low carbon steel. This process consists of two successive deformations by extrusion and ECAP in a single die （Ex-ECAP）. Cylindrical samples were heated to predefined temperatures （650 and 850 ℃） and then pressed through a die channel with crosshead speed of 10 mm/s. Microstructure and resultant mechanical properties of processed material were studied. The results showed that pressing temperature has a significant effect on the resultant microstructure. While at 650 ℃, the cold worked structure with elongated ferrite grains were obtained, and at 850 ℃ the microstructure consisted of elongated ferrite grains and very fine grains at their boundaries as a consequence of continuous dynamic recrystallization （CDRX） of ferrite phase. Also at 850 ℃, a particular microstructure consisted of cold worked ferrite and static recrystallized grains on shear bands was obtained.展开更多
Grain refinement in a plain carbon steel under intercritical warm deformation was studied by torsion tes ring. Based on the experimental results, the warm flow behaviour and microstructural evolution of ferrite were r...Grain refinement in a plain carbon steel under intercritical warm deformation was studied by torsion tes ring. Based on the experimental results, the warm flow behaviour and microstructural evolution of ferrite were researched with particular emphasis on the effect of the strain rate in controlling the grain refinement mechanism of fer- rite. The deformed microstructures were investigated at various strain rates using optical microscopy and electron back-scattered diffraction （EBSD）. The EBSD observations indicate that an increase in the strain rate leads to the development of new fine ferrite grains with high angle boundaries. Furthermore, it shows that the annihilation of dislo- cations occurs more readily at lower strain rate. The elongated ferrite grains continuously dynamically recrystallize to form the equiaxed fine ferrite grains. Thereby, the aspect ratio of elongated grains decreases with increasing the strain rate. Furthermore, the peak stress and steady state stress of ferrite both increase with increasing strain rate. Based on the study, the effect of strain rate on the development of fine ferrite grains during continuous dynamic recrystallization of ferrite was analyzed in detail.展开更多
文摘A combination of extrusion and equal channel angular pressing （ECAP） was used to deform a plain low carbon steel. This process consists of two successive deformations by extrusion and ECAP in a single die （Ex-ECAP）. Cylindrical samples were heated to predefined temperatures （650 and 850 ℃） and then pressed through a die channel with crosshead speed of 10 mm/s. Microstructure and resultant mechanical properties of processed material were studied. The results showed that pressing temperature has a significant effect on the resultant microstructure. While at 650 ℃, the cold worked structure with elongated ferrite grains were obtained, and at 850 ℃ the microstructure consisted of elongated ferrite grains and very fine grains at their boundaries as a consequence of continuous dynamic recrystallization （CDRX） of ferrite phase. Also at 850 ℃, a particular microstructure consisted of cold worked ferrite and static recrystallized grains on shear bands was obtained.
文摘Grain refinement in a plain carbon steel under intercritical warm deformation was studied by torsion tes ring. Based on the experimental results, the warm flow behaviour and microstructural evolution of ferrite were researched with particular emphasis on the effect of the strain rate in controlling the grain refinement mechanism of fer- rite. The deformed microstructures were investigated at various strain rates using optical microscopy and electron back-scattered diffraction （EBSD）. The EBSD observations indicate that an increase in the strain rate leads to the development of new fine ferrite grains with high angle boundaries. Furthermore, it shows that the annihilation of dislo- cations occurs more readily at lower strain rate. The elongated ferrite grains continuously dynamically recrystallize to form the equiaxed fine ferrite grains. Thereby, the aspect ratio of elongated grains decreases with increasing the strain rate. Furthermore, the peak stress and steady state stress of ferrite both increase with increasing strain rate. Based on the study, the effect of strain rate on the development of fine ferrite grains during continuous dynamic recrystallization of ferrite was analyzed in detail.
