TY - GEN
T1 - Formation of ultrafine grained ferrite by warm deformation of tempered lath martensite in low alloy steels
AU - Poorganji, B.
AU - Yamaguchi, T.
AU - Maki, T.
AU - Miyamoto, G.
AU - Furuhara, T.
PY - 2007/1/1
Y1 - 2007/1/1
N2 - Microstructure change during warm deformation of tempered lath martensite in Fe-2mass%Mn-C alloys with different carbon contents in the range between 0.1 and 0.8mass%C was investigated. Specimens of the alloys after being quenched and tempered at 923K for 0.3ks were compressed by 50% with a strain rate varying from 10-3 to 10"V at 923K. EBSD analysis of the deformed microstructures has revealed that fine equiaxed ferrite (a) grains surrounded by high-angle boundaries are formed by dynamic recrystallization (DRX). As carbon content increases, the DRX a grain size decreases. This could be attributed to the change in volume fraction of the cementite (6) phase as boundary dragging particles. The sub-micron 9 particles can suppress the coarsening of the DRX a grains by exerting a pinning effect on grain boundary migration. Furthermore, the fraction of recrystallized region increases by increasing carbon content, presumably due to a decrease in the martensite block width as an initial a grain size and a larger volume fraction of hard second phase (6) particles. Both of these should increase inhomogeneous plastic deformation which promotes the recrystallization. It seems that continuous DRX is responsible for the formation of ultrafine a grains in the tempered lath martensite.
AB - Microstructure change during warm deformation of tempered lath martensite in Fe-2mass%Mn-C alloys with different carbon contents in the range between 0.1 and 0.8mass%C was investigated. Specimens of the alloys after being quenched and tempered at 923K for 0.3ks were compressed by 50% with a strain rate varying from 10-3 to 10"V at 923K. EBSD analysis of the deformed microstructures has revealed that fine equiaxed ferrite (a) grains surrounded by high-angle boundaries are formed by dynamic recrystallization (DRX). As carbon content increases, the DRX a grain size decreases. This could be attributed to the change in volume fraction of the cementite (6) phase as boundary dragging particles. The sub-micron 9 particles can suppress the coarsening of the DRX a grains by exerting a pinning effect on grain boundary migration. Furthermore, the fraction of recrystallized region increases by increasing carbon content, presumably due to a decrease in the martensite block width as an initial a grain size and a larger volume fraction of hard second phase (6) particles. Both of these should increase inhomogeneous plastic deformation which promotes the recrystallization. It seems that continuous DRX is responsible for the formation of ultrafine a grains in the tempered lath martensite.
KW - Dynamic recrystallization
KW - Lath martensite
KW - Ultrafine grain
KW - Warm deformation
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U2 - 10.4028/0-87849-443-x.557
DO - 10.4028/0-87849-443-x.557
M3 - Conference contribution
AN - SCOPUS:38349095375
SN - 087849443X
SN - 9780878494439
T3 - Materials Science Forum
SP - 557
EP - 562
BT - Recrystallization and Grain Growth III - Proceedings of the Third International Conference on Recrystallization and Grain Growth, ReX and GG III
PB - Trans Tech Publications Ltd
T2 - 3rd International Conference on Recrystallization and Grain Growth, ReX GG III
Y2 - 10 June 2007 through 15 June 2007
ER -