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引言等温淬火球铁(ADI)具有强度与韧性的显著结合,是由于原奥氏体等温转变成类似贝氏体的产物。这一转变过程由于高碳奥氏体分解的动力学和合金元素的偏析而复杂化了。在通常条件下,ADI所要求的显微组织是由高碳奥氏体基体和分布在其间的铁素体(或铁素体加碳化物)片所组成。这种组织的形成可由图1 Fe—C—Si三元等浓度示意图来说明。奥氏体化温度T_γ和γ/γ+石墨的相界位置决定奥氏体化后的含碳量C°_γ,在250℃～450℃温度范围内淬火时,随着铁素体在奥氏体中形核和长大的同时,碳被排到奥氏体中,在高碳奥氏体(图1中
INTRODUCTION The combination of strength and ductility of austempered ductile iron (ADI) is due to the isothermal transformation of the former austenite into a bainite-like product. This process of transformation is complicated by kinetics of high-carbon austenite decomposition and segregation of alloying elements. Under normal conditions, the microstructure required by ADI consists of a high-carbon austenitic matrix with ferrite (or ferritic plus carbide) flakes distributed between them. The formation of this kind of structure can be illustrated by the ternary concentration diagram of Fe-C-Si in Figure 1. Austenitization temperature T_γ and γ / γ + graphite phase boundary determine the carbon content after austenitizing C ° _γ, quenching in the temperature range of 250 ℃ ~ 450 ℃, with the ferrite in the austenitic While nucleating and growing in the body, the carbon is discharged into the austenite and in the high-carbon austenite (Figure 1