Spontaneous Reverse Transformation due to Adiabatic Deformation Heating in 0.3%C-9%Ni Steel

Grain Structure of Fe-0.3mass%C-9mass%Ni Steel Processed through .ALPHA..RAR..GAMMA..RAR..ALPHA.' Transformation Caused by Spontaneous Reverse Transformation

“…8) It is reasonable because observed plate surface temperature which is almost same as the temperature at the mid-thickness 8) was higher than Ae 3 transformation temperature. Figure 4 shows microstructures of the rolled plate taken at mid-thickness and quarter-thickness (un-tempered condition).…”

“…Very randomised grain structure including ND//͗1 1 0͘ a grains at the quarter-thickness obtained in this study can be qualitatively explained by this phenomenon, because equivalent strain remarkably increases toward the plate surface due to shear strain component introduced by the rolling pass conducted in this study. 8) It can be understood that the random grain structure at the quarterthickness would result from initial ferrite rolling texture originally developed under the existence of shear strain before a → g → aЈ transformation.…”

“…6) The new process, so called "Spontaneous Reverse Transformation (SRT)", has already been demonstrated. [7][8][9] Final martensite (aЈ) grain size (prior austenite grain size or packet size) with less than 1 mm has been obtained through a → g → aЈ transformation caused by SRT in Fe-0.3C-9Ni mass% steel. 7) Thus, SRT is the process to have an ultra refined austenite, and resulting ultra refined transformation products such as ferrite, bainite and martensite effectively.…”

Reverse Transformation Caused by Temperature Increase due to Deformation Heating

“…SRT occurs due to adiabatic heating caused by a deformation at temperatures close to the austenite phase field. It has been observed in rolling experiments [3][4][5] as well as in uniaxial compression tests. 1,2) SRT has been developed as a microstructural control process to obtain ultrafine grained steels.…”

“…The ferrite (a) to austenite (g) reverse transformation can also be induced by an internal heat source, for example a temperature increase due to deformation heating. Spontaneous reverse transformation (SRT) [1][2][3][4][5] and transformed shear band (TSB) [6][7][8][9][10][11] are two such cases. SRT occurs due to adiabatic heating caused by a deformation at temperatures close to the austenite phase field.…”