Thermal Stability of Austempered Ductile Iron Evaluated in a Temperature Range of 20-300K

Abstract

The aim of this article was to determine through changes in magnetic properties the stability of the austempered ductile iron (ADI) microstructure during temperature changes in a range of 20 – 300 K. The measurements were taken in a vibrating sample magnetometer (VSM) using Fe27Ni2TiMoAlNb austenitic stainless steel and four types of austempered ductile iron obtained under various heat treatment conditions. The plotted curves showing changes in the magnetisation degree as a function of temperature had a number of characteristic points illustrating changes taking place in the microstructure. For each of the materials examined, the martensite start temperature Ms and the temperature range within which the martensitic transformation takes place were identified.

Keywords

• austempered ductile iron, cryogenic treatment, thermal stability, martensitic transformation