%0 Journal Article %T Effect of sub-zero cooling on microstructure and mechanical properties of a low alloyed austempered ductile iron %A S. Yazdani %A M. Ardestani %J China Foundry %D 2007 %I Foundry Journal Agency %X The effect of sub-zero cooling on microstructure and mechanical properties of a low alloyed austempered ductile iron has been investigated. Austempering of samples was performed at 325! and 400¡æ after austenitizing at 875¡æ and 950¡æ. The sub-zero treatments were carried out by cooling down the samples to -30¡æ, -70¡æ and -196¡æ. The changes in volume fraction of austenite and mechanical properties were determined after cooling to each temperature. The austenite volume fraction of samples which were austenitized at 875¡æ and austempered at 325¡æ remained unchanged, whilst it reduced in samples austenitized at 950¡æ and 875¡æ for austempering temperature of 400¡æ. In these specimens, some austenite transformed to martensite after subzero cooling. Mechanical property measurements showed a slight increase in strength and hardness and decrease in elongation and toughness due to this transformation behavior. %K austempered ductile iron %K austenite %K sub-zero cooling %K martensitic transformation %K ausferrite %U http://www.foundryworld.com/uploadfile/2008111840961377.pdf