ABSTRACT Austempered Ductile Irons (ADIs) with different contents of nickel and copper were austenitized at the same conditions, and austempered for 60, 90 and 180 min to investigate the austempering evolution. Besides the conventional ductility analysis to assess the best austempering times, strain hardening analysis of tensile flow curves was carried out, since it has been found reliable for this assessment if dislocation-density-related constitutive equations are used. Through plotting the Voce equation parameters 1/εc vs. ϴo found from the strain hardening analysis, Matrix Assessment Diagrams (MADs) were drawn, and austempering conditions closest to the best austempering times were identified. Austempering times found with ductility-criterion and MAD approach did not match. Mg–Cu particles found in copper-containing ADIs affected the reliability of tensile ductility that could not be ascribed to ausferrite stability only, while the austempering times found with MAD approach seemed to be consistent with solid-state diffusion transformations.

中文翻译：

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延展性检查与基于应变硬化分析的新方法之间的比较，以支持确定适当的等温回火时间

摘要 在相同条件下对镍和铜含量不同的奥氏体球墨铸铁 (ADI) 进行奥氏体化处理，然后进行 60、90 和 180 分钟的奥氏体回火以研究奥氏体回火演变。除了用于评估最佳等温回火时间的常规延展性分析外，还进行了拉伸流动曲线的应变硬化分析，因为如果使用与位错密度相关的本构方程，则已发现该评估可靠。通过绘制从应变硬化分析中发现的 Voce 方程参数 1/εc 与 ϴo，绘制了矩阵评估图 (MAD)，并确定了最接近最佳等温回火时间的等温回火条件。使用延展性标准和 MAD 方法发现的等温回火时间不匹配。