Deformation Behaviour of Ultrafine Grained Steel Produced by Cold Rolling of Martensite

Toward unraveling the mechanisms responsible for the formation of ultrafine grained microstructure during tempering of cold rolled martensite

“…0.5 h at 500 °C) to produce ferrite grain size of ~ 180 nm [3]. 2 The effects of tempering temperature [3], rolling reduction [4], microalloying elements [5], tempering time [6], and other deformation modes [7] have been studied so far and the main focus has been on the obtained grain sizes. However, the mechanism responsible for the formation of ultrafine microstructure is still under debate [5].…”

“…Many techniques based on severe plastic deformation and advanced thermomechanical processing have been proposed so far for grain refinement of metallic materials [2]. Thermomechanical processing on a martensite starting microstructure is claimed to be an efficient grain refining approach in low carbon steels [3][4][5][6][7], which normally includes simple rolling that requires low reductions in thickness (~ 50%) followed by short tempering at moderate temperatures (e.g. 0.5 h at 500 °C) to produce ferrite grain size of ~ 180 nm [3].…”

“…The evolution of hardness during tempering of cold rolled martensite 6. Continued tempering at 550 °C up to 45 min brings another distinct stage (Stage II), where the tensile strength level decreases by ~ 90 MPa as a result of coarsening of the lamellar microstructure as can be seen in…”

Tempering of deformed and as-quenched martensite in structural steel

“…Based on this fact, an advanced thermomechanical processing has been developed by Tsuji et al [26], which is based on the rolling of a martensite starting microstructure followed by short tempering to produce an ultrafine ferrite/carbide aggregate. Several excellent works have been reported on this subject: the effects of rolling reduction and tempering temperature have been studied by Ueji et al [27,28]; the effect of microalloying elements has been reported by Lan et al [29]; and the effect of tempering time has been revealed by Malekjani et al [30]. However, the formation mechanism of ultrafine microstructure has received less attention and it is reported to be still under debate by Lan et al [29] and Najafi et al [14].…”