Influência do alumínio nas propriedades mecânicas do ADI (Austempered Ductile Iron)

Abstract

The ADI (Austempered Ductile Iron), a cast iron obtained after the proper heat treatment of regular sheroidal graphite iron, has been intensely studied in the last years. Silicon is the standard element added for graphitization of the alloy. In this study it was replaced by aluminium, an element know as presenting a similar chemical behavior in the alloy. Themelting procedure was the same as the used in the production of the standard ADI-Si. The aluminium content, replacing part of the silicon, were 0,75; 2,26 and 2,99% Al. The austempering temperatures were 270, 320, 370°C. The testing specimens were obtained according ASTM A 897 and regular tensile and hardness tests were used to determine the mechanical properties of the alloy with non-reacted austenite and carbide precipitation. The mechanical properties degenerated, accordingly, establishing the need of the use of a special melting procedure when dealing with this Al-bearing alloy.