Abstract: Carbide formation in austempered ductile iron (ADI) alloyed with Ni and Cu has been studied by use of TEM. The results show that η carbide precipitates in the bainitic ferrite when austempered at 350℃.for 6h, but no carbide was found at the austenite/.ferrite interfaces. When austempered at 300℃, two kinds of. s carbides appear in the bainitic ferrite when austempering time reached I h, and X carbide also precipitates at the austenite /ferrite interfaces when austempering time was extended up to 6h. The bainitic. ferrite and the retained austenite follow the Nishiyama- Wasserman relationship,

Key words: carbide, austempered ductile iron