INVESTIGATION OF THE AUSTENITE-BAINITE TRANSFORMATION IN GRAY IRON USING REAL-TIME NEUTRON TRANSMISSION

In globulitic gray iron (3.6 wt.% C, 2.4 wt.% Si and 0.45 wt.% Mn) the decomposition of austenite into bainite is investigated in real time using a new method based on neutron scattering. During the phase trans formation transmission spectra of thermal neutrons are continuously re corded containing specific Bragg edges. Thus, the transformation is fo llowed in-situ time resolved by evaluating the relative (micro)structu ral fractions of the transforming phases from the heights of the corre sponding Bragg edges. The progression of the transformation is describ ed and the results are discussed. The observed late time deviations fr om the Avrami law are explained by residual stresses of the second kin d (homogeneous microstresses), which occur during the transformation b ecause of the different specific volumes of the phases.