Isothermal Grain Growth of Austenite in Hypoeutectoid and Hypereutectoid Plain Carbon Steels

Grain growth kinetics of austenite in a hypoeutectoid steel (containing carbon of 0.35%) at 920 °C and in a hypereutectoid steel (containing carbon of 1%) at 980 °C for holding time ranging from 1 h to 6 h was investigated. The hypoeutectoid steel exhibited normal grain growth without solute drag hindrance with a time exponent (0.51) close to the theoretical value (0.5). However, the grain growth of austenite in the hypereutectoid steel held up to 3 h was extremely slow, characterizing by a low value of time exponent (0.08). Thereafter, a breakaway occurred and the grain growth in the hypereutectoid steel held from 3 h to 6 h progressed normally with a time exponent (0.52) close to the theoretical value (0.5).