The effect of the austenitization route on the bainitic reaction kinetics of an alloyed (3.2C–2.8Si–1.8Ni–1.4Cu–0.4Mn–0.2Mo–0.1Cr) austempered ductile iron was studied. Two-step, conventional and rapid austenitization heat treatments were employed to produce different austenite grains sizes (94, 39, and 15 μm, respectively) and, in one case, secondary graphite precipitation. The overall bainitic transformation kinetic at 350 °C was described using the Johnson-Mehl-Avrami-Kolmogorov equation, and the values of the Avrami's adjustable parameters were discussed. The austempering reaction of the coarser austenite microstructure with secondary graphite precipitation featured the fastest kinetics, while the one derived from the medium austenite grain showed the slowest reaction rate. The increase in the graphite/austenite interfacial area reduced the half-transformation time (t₅₀-value) by one magnitude compared to the austenite grain boundary area. The austempered samples from the rapid austenitization route comparatively featured the best tensile properties and the highest ISO and ASTM standards grades despite the considerable proportion of grain boundary allotriomorphic ferrite.

研究了奥氏体化途径对合金化（3.2C–2.8Si–1.8Ni–1.4Cu–0.4Mn–0.2Mo–0.1Cr）奥氏体球墨铸铁贝氏体反应动力学的影响。采用两步，常规和快速奥氏体热处理来产生不同的奥氏体晶粒尺寸（分别为94、39和15μm），在一种情况下，还产生二次石墨析出。使用Johnson-Mehl-Avrami-Kolmogorov方程描述了在350°C时的整体贝氏体转变动力学，并讨论了Avrami可调参数的值。较粗的奥氏体组织与二次石墨析出的奥氏体回火反应动力学最快，而中奥氏体晶粒的奥氏体反应速度最慢。与奥氏体晶界区域相比降低_50个值）。尽管晶界同素异形铁素体的比例很大，但来自快速奥氏体化途径的奥氏体样品具有最佳的拉伸性能和最高的ISO和ASTM标准等级。