한국주조공학회

The effects of heat treatments and alloying elements on the microstructure and mechanical charaterisitics of specially austempered ADIs containing alloying elements such as Cu, Mo and Ni were investigated. To compare with the effect of conventional and normal(CN) austempering treatment, two kinds of special austempering treatments which are those with pre-quenching and pre-heating were conducted. The hardness and uniaxial fatigue tests were carried out to evaluate the mechanical charateristics. The hardness of ADI treated by CN heat cycles was higher than those of other ADIs. Cu added ADI (Cu-ADI) tempered at 400 after austenitizing exhibited the highest fatigue life cycles. While austempering after prequenching makes the austenite with high carbon stable, which resulted in transformation to highly strengthened bainites from the carbon enriched austenite phases during tempering. The high carbon enriched banites is considered to improve the fatigue strength.

Heat treament cycle, Prequenching austernpering,Fatigue test, Preheating austempering, Fatigue life cycles, Fatigue strength