Physio-Mechanical Investigation of Austempered Ductile Iron

Abstract

The results of experimental (physical and mechanical) study of Austempered Ductile Iron (ADI) are presented. The aim of the investigation is to locally produce ADI and to have a closer look into the mechanical properties of this very attractive cast material. The experiment was carried out with ASTM A536 Grade Ductile Cast Iron, which was first produced using a high frequency dual track induction furnace of 2500kg capacity by adding small quantities of magnesium alloy to a base cast iron with essentially the same analysis as grey cast iron, which produces graphite speroids instead of flakes. The ductile cast iron samples were subsequently subjected to a specific parameter of heat treatment – Austenitizing (930^oC for 140 minutes) and Austempering (370^oC for 10 minutes) in Potassium nitrate salt bath to give ADI. Mechanical test (Tensile) is conducted on the ductile iron and ADI specimen using Universal Testing Machine (Instron - Series 3369) to evaluate the basic mechanical properties (yield stress, tensile strength and elongation). Structure of the specimens was studied with conventional metallography. It followed from the study that ductile iron properties were significantly improved after heat treatment, elongation increased by 27.04% and tensile strength by 58.62%.

Keywords: Austempered Ductile Iron, A536 Grade Ductile Cast Iron, Heat Treatment, Tensile Strength, Elongation, Metallography.