Microstructural Path Analysis of Martensite Dimensions in FeNiC and FeC Alloys

Athermal Martensite Transformation Curve

“…The mean value of the fitted E A values was E A ≅ 10 -20 J/event that is in good agreement with the value obtained in our previous work 23 and compares with the activation energy for dislocation processes in austenite 23 for a detailed discussion of this.…”

“…The model includes a thermal activated martensite plate volume. This is supported by the previous finding 23 of a thermal activated martensite thickness. We attributed this thermal activated term to the drag effect of the austenite plasticity on the mobility of the martensite-austenite interface.…”

“…In a recent work 23 , the present authors examined in detail the temperature dependence of the mean "intrinsic" (or extended) dimensions of the martensite units in Fe-31wt%Ni-0.02wt%C. The conclusions were that the diameter, D, remained roughly temperature independent and scaled with the grain size (the martensite partitions the austenite grains) whereas the thickness, t, decreased with temperature with an Arrhenius like temperature dependence…”

“…The dislocations introduced in the adjacent austenite to assist in the relaxation of the transformation strains interact with the mobile athermal martensite-austenite interface. Notice that whereas dislocation processes in the austenite are thermally activated processes, the martensite-austenite interface movement itself is not regarded to be thermally activated 23 . The comparison of the model, equation 9 with experimental data permits the following conclusions:…”

“…In this paper, considering that martensite extended thickness is thermally activated 23 we propose that the martensite extended volume, v M = πtD 2 /4, is also thermally activated…”