Displacive Mechanism of Bainitic Formation in Carbon-Depleted Region of Austenite

In-situ observations of lattice parameter fluctuations in austenite and transformation to bainite

“…After 300 seconds of isothermal hold, the carbon-poor austenite region corresponds to 0.62 wt pct C and the carbon-rich austenite to 1.03 wt pct C. It is interesting that the ferrite carbon concentration ranges from 0.40 to 0.62 wt pct. This may be because it is the low-carbon austenite that transforms first, an interpretation, which would be consistent with the suggestions of Klier and Lyman, [5] Entin, [6] and recently by Wu et al [11] …”

“…[3,4] Historically, it has also been speculated that the austenite becomes heterogeneous with carbon-enriched and carbon-depleted regions, so that ferrite formation initiates in the carbon-depleted regions. [5][6][7][8][9][10][11] In the present work, it has been possible to follow the lattice parameter changes associated with the austenite at any temperature and during the course of the bainite transformation. If the changes can be attributed to solute concentration, then they help interpret the role of carbon.…”