Nb tubes were fabricated through hydrostatic extrusion at extrusion ratios of 3.1 and 6.1 at ambient temperature,and then their microstructure,texture,and Vickers hardness were investigated based on electron back-scat...Nb tubes were fabricated through hydrostatic extrusion at extrusion ratios of 3.1 and 6.1 at ambient temperature,and then their microstructure,texture,and Vickers hardness were investigated based on electron back-scattered diffraction(EBSD)data.The fraction of low-angle boundaries(LABs)largely decreased with a sharp decrease in mean grain sizes after hydrostatic extrusion and was not proportional to extrusion ratios,assuming that mixed-asymmetrical junctions forming LABs dissociate at high extrusion ratios from the external stress(>981 MPa)with thermal activation by the generated heat.The correlation between grain size and Vickers hardness followed the Hall−Petch relationship despite the texture gradient of theá111ñcyclic fiber textural microstructure at low extrusion ratios and theá100ñtrue fiber textural microstructure at high extrusion ratios.The increase in hydrostatic pressure on the Nb tubes contributed to texture evolution in terms of extrusion ratios due to the difference between{110}<111>and{112}<111>components based on EBSD data.展开更多
基金supported by a Grant from the Fundamental R&D Program(10067694)funded by the Ministry of Trade,Industry and Energy,Korea。
文摘Nb tubes were fabricated through hydrostatic extrusion at extrusion ratios of 3.1 and 6.1 at ambient temperature,and then their microstructure,texture,and Vickers hardness were investigated based on electron back-scattered diffraction(EBSD)data.The fraction of low-angle boundaries(LABs)largely decreased with a sharp decrease in mean grain sizes after hydrostatic extrusion and was not proportional to extrusion ratios,assuming that mixed-asymmetrical junctions forming LABs dissociate at high extrusion ratios from the external stress(>981 MPa)with thermal activation by the generated heat.The correlation between grain size and Vickers hardness followed the Hall−Petch relationship despite the texture gradient of theá111ñcyclic fiber textural microstructure at low extrusion ratios and theá100ñtrue fiber textural microstructure at high extrusion ratios.The increase in hydrostatic pressure on the Nb tubes contributed to texture evolution in terms of extrusion ratios due to the difference between{110}<111>and{112}<111>components based on EBSD data.
