Abnormal α to γ Transformation Behavior of Steels with a Martensite and Bainite Microstructure at a Slow Reheating Rate

<i>In Situ</i> EBSD Analysis on the Crystal Orientation Relationship between Ferrite and Austenite during Reverse Transformation of an Fe-Mn-C Alloy

“…The mechanism of variant selection of transforming γ has been discussed in the literature. In studies on the texture memory effect during α−γ−α transformation [14][15][16][17][18][19][20][21][22] , it is commonly suggested that the γ texture after the reverse transformation is not randomly selected but is determined under the rule on the variant selection of transforming γ. Various models to explain the variant selection rules of transforming γ during reverse transformation have been proposed.…”

Temperature Dependence of Austenite Nucleation Behavior from Lath Martensite

“…[2][3][4][5][6] Authors also confirmed in the previous study that the reversed austenite preferentially nucleated at LBs rather than prior austenite grain boundaries (PAGBs) in 13%Cr-6%Ni martensitic stainless steel reversion-treated at 913 K. 7) On the contrary, some researchers reported that the nucleation behavior of austenite was influenced by the heating rate in low carbon steels; acicular austenite grains were frequently formed within a prior austenite grain under a low heating rate, while the granular ones tended to be formed mainly on PAGBs when the heating rate was increased. [2][3][4][5][6] This result suggests that the shape and nucleation site of reversed austenite would depend on the temperature at which the nucleation occurs. Since the size and dispersion of austenite nuclei affect the final microstructure after completion of reversion, it is necessary to understand the nucleation behavior for controlling mechanical properties of steels.…”

Reversed Austenite Growth Behavior of a 13%Cr-5%Ni Stainless Steel during Intercritical Annealing

“…4) The nucleation and growth of reversed austenite during heating process are regarded to play critical roles in "austenite memory". [5][6][7][9][10][11][12][13]17) In order to make clear the mechanisms of "austenite memory", it's critical to investigate the formation mechanism of the reversed austenite.…”

“…5,8,11,[13][14][15][16][18][19][20][21] It is commonly accepted that there are two kinds of reversed austenite formation mechanisms, namely "acicular" and "globular" mechanisms, respectively. Globular austenite tends to nucleate at original austenite grain boundaries or inside the lathes with substrate of precipitates, thus disintegrate the original austenite grain and lead to grain refinement 11,13,16,18) In the "acicular" mechanism, acicular austenite nucleates at lath boundaries and has a K-S orientation relationship with the matrix, and recovery of original austenite grain happens after phase transformation.…”

“…5,8,11,[13][14][15][16][18][19][20][21] It is commonly accepted that there are two kinds of reversed austenite formation mechanisms, namely "acicular" and "globular" mechanisms, respectively. Globular austenite tends to nucleate at original austenite grain boundaries or inside the lathes with substrate of precipitates, thus disintegrate the original austenite grain and lead to grain refinement 11,13,16,18) In the "acicular" mechanism, acicular austenite nucleates at lath boundaries and has a K-S orientation relationship with the matrix, and recovery of original austenite grain happens after phase transformation. 11,13,14,16,18) However, there is still a demand for more comprehensive investigations for the formation mechanism of the reversed austenite, since possible factors that affect the nucleation and growth behaviors of reversed austenite are complicated, for instance, Ni/Cr ratio, 6) C content, 2) heating rate, 3) intercritical annealing temperature 5) and so on.…”