This work presents the qualitative and quantitative changes in the products of isothermal transformation (reaction) in a ductile cast iron
austenite after supercooling to the temperature range Ar1. The austenitizing temperature considered in this work was 900, 960 or 1020°C.
The eutectoid reaction was investigated by metallographic examination at a holding temperature right below Ar11 (820°C) or right below
Ar12 (760°C). The quantitative metallographic examination was carried out with a light microscope (LM). The initial transformation stage
products were identified with a transmission electron microscope (TEM). The selected samples were studied for chemical
microsegregation of manganese, silicon, phosphorus, and carbon with an X-ray microanalyser (MAR). The tested cast iron material was
found to predominantly feature a eutectoid reaction in the metastable system the ratio of which was increasing with the austenitizing
temperature. The austenitizing temperature was found to be conducive to the evolution kinetics of individual phases and to the
graphitization kinetics of the eutectoid cementite that was formed during the contemplated reaction.
One type of spheroidal cast iron, with additions of 0.51% Cu and 0.72% Ni, was subjected to precipitation hardening. Assuming that the
greatest increase in hardness after the shortest time of ageing is facilitated by chemical homogenisation and fragmentation of cast iron
grain matrix, precipitation hardening after pre-normalisation was executed. Hardness (HB), microhardness (HV), qualitative and
quantitative metalographic (LM, SEM) and X-ray structural (XRD) tests were performed. The acquired result of 13.2% increase in
hardness after ca. 5-hour ageing of pre-normalised cast iron confirmed the assumption.
This scientific paper presents the research on influence of austenitizing temperature on kinetics and evolution of the spheroidal plain cast
iron during eutectoid reaction in isothermal conditions. The cast iron has been austenitized in temperatures of 900, 960 or 1020°C. There
were two temperature values of isothermal holding taken into consideration: 760 or 820°C. The order of creation of reaction products and
their morphology have been analyzed. The particular attention has been paid to the initial stage of transformation. The qualitative research
has been executed using the transmission electron microscope (TEM), as well as quantitative research (LM). The influence of austenitizing
temperature has also been determined on transformation kinetics and structural composition. It was found that the increase of austenitizing
temperature is conductive to the initial release of structures by metastable system. A reduction of time was observed of the initial stage of
transformation at temperature close to Ar12 with its simultaneous elongation at temperature close to Ar11, with an increase of austenitizing
temperature. The dependences obtained by the metallographic method confirm the prior results of dilatometric research of eutectoid
reaction.