Solid state transformations in ductile iron—influence of prior austenite matrix microstructure

The decomposition of austenite after different cooling rates has been studied for unalloyed and alloyed ductile iron. The influence of the austenite microstructure was evaluated. Jominy like tests were carried out on samples shaken out from the mold at temperature below the eutectoid range, and on samples austenitized conventionally. The hot shaken out samples show greater hardenability than conventionally reheated samples. This is caused by the much larger grain size displayed by the austenite during the post-solidification cooling. The matrix microstructure was evaluated along the length of the Jominy samples. Different growth patterns of ferrite were identified. A continuous transformation diagram for ductile iron was proposed.