TY - JOUR
T1 - Origin of significant grain refinement in Co-Cr-Mo alloys without severe plastic deformation
AU - Yamanaka, Kenta
AU - Mori, Manami
AU - Chiba, Akihiko
N1 - Funding Information:
This research was financially supported by the Global COE Program ‘‘Materials Integration (International Center of Education and Research), Tohoku University,’’ a Grant-in-Aid for Scientific Research (B), and the Regional Innovation Cluster Program from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.
PY - 2012/12
Y1 - 2012/12
N2 - We have previously reported that ultrafine-grained (UFG) microstructures can be obtained in a Co-29Cr-6Mo (wt pct) alloy by utilizing dynamic recrystallization (DRX) that occurs during conventional hot deformation (Yamanaka et al.: Metall. Mater. Trans. A, 2009, vol. 40A, pp. 1980-94). The present study investigates the novel DRX mechanism of this alloy in detail. The microstructure evolution during hot deformation under relatively high Zener-Hollomon (Z) parameter conditions for which ultrafine grains can develop was systematically investigated by electron backscatter diffraction (EBSD) and transmission electron microscopy. This alloy exhibited a different flow stress behavior and microstructural development from conventional DRX mechanisms. The deformation microstructure contained a large number of stacking faults, which implies that planar dislocation slip is the primary deformation mechanism in the hot deformation of the Co-29Cr-6Mo alloy due to its abnormally low stacking fault energy (SFE) at elevated temperatures. Inhomogeneities in local strain distributions induced by planar slip will enhance grain subdivision by geometrically necessary (GN) dislocation boundaries. Deformation twinning may also contribute to grain refinement. The DRX mechanism operating in the Co-29Cr-6Mo alloy is discussed by considering the relationships between anomalous dislocation structures, flow stress behavior, texture development, and nucleation behavior.
AB - We have previously reported that ultrafine-grained (UFG) microstructures can be obtained in a Co-29Cr-6Mo (wt pct) alloy by utilizing dynamic recrystallization (DRX) that occurs during conventional hot deformation (Yamanaka et al.: Metall. Mater. Trans. A, 2009, vol. 40A, pp. 1980-94). The present study investigates the novel DRX mechanism of this alloy in detail. The microstructure evolution during hot deformation under relatively high Zener-Hollomon (Z) parameter conditions for which ultrafine grains can develop was systematically investigated by electron backscatter diffraction (EBSD) and transmission electron microscopy. This alloy exhibited a different flow stress behavior and microstructural development from conventional DRX mechanisms. The deformation microstructure contained a large number of stacking faults, which implies that planar dislocation slip is the primary deformation mechanism in the hot deformation of the Co-29Cr-6Mo alloy due to its abnormally low stacking fault energy (SFE) at elevated temperatures. Inhomogeneities in local strain distributions induced by planar slip will enhance grain subdivision by geometrically necessary (GN) dislocation boundaries. Deformation twinning may also contribute to grain refinement. The DRX mechanism operating in the Co-29Cr-6Mo alloy is discussed by considering the relationships between anomalous dislocation structures, flow stress behavior, texture development, and nucleation behavior.
UR - http://www.scopus.com/inward/record.url?scp=84872013162&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84872013162&partnerID=8YFLogxK
U2 - 10.1007/s11661-012-1303-5
DO - 10.1007/s11661-012-1303-5
M3 - Article
AN - SCOPUS:84872013162
SN - 1073-5623
VL - 43
SP - 4875
EP - 4887
JO - Metallurgical Transactions A (Physical Metallurgy and Materials Science)
JF - Metallurgical Transactions A (Physical Metallurgy and Materials Science)
IS - 12
ER -