Improvement in strength and toughness of austempered ductile cast iron by a novel two-step austempering process
Improvement in strength and toughness of austempered ductile cast iron by a novel two-step austempering process
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DOI：
10.1016/j.matdes.2003.09.021
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发表时间：
2004-05
影响因子：
8.4
通讯作者：
Jianghuai Yang;S. Putatunda
中科院分区：
文献类型：
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作者：
Jianghuai Yang;S. Putatunda
奥贝球铁（ADI）因其优异的力学性能，近年来已成为一种重要的工程材料。这些特性包括具有良好延展性的高强度、良好的耐磨性、疲劳强度和断裂韧性。因此，它被认为是锻造钢或锻钢的经济替代品，用于多种结构应用，特别是汽车工业。在这项调查中，一个球或球墨铸铁与主要珠光体铸态组织处理的一种新的两步等温淬火工艺。制备了两批样品。所有样品最初在927 ° C（1700 ° F）下恒温2小时。第一批样品通过常规的单步等温淬火工艺在几个温度下进行处理，例如260 ° C（500 ° F）、273 ° C（525 ° F）、288 ° C（550 ° F）、302 ° C（575 ° F）、316 ° C（600 ° F）、330 ° C（625 ° F）、343 ° C（650 ° F）、357 ° C（675 ° F）、371 ° C（700 ° F）、385 ° C（725 ° F）和400 ° C（750 ° F）处理2小时，而第二批样品通过两步等温淬火工艺处理。这些样品最初在保持在260 ° C（500 ° F）的盐浴中淬火5分钟，然后在几个等温淬火温度下等温淬火2小时。这些温度分别为288 ° C（550 ° F）、302 ° C（575 ° F）、316 ° C（600 ° F）、330 ° C（625 ° F）、343 ° C（650 ° F）、357 ° C（675 ° F）、371 ° C（700 ° F）、385 ° C（725 ° F）和400 ° C（750 ° F）。研究了两步等温淬火工艺对奥贝球铁显微组织和力学性能的影响。试验结果表明，与传统的一步等温淬火工艺相比，两步等温淬火工艺显著提高了材料的屈服强度、抗拉强度和断裂韧性。
Austempered ductile cast iron (ADI) has emerged as an important engineering material in recent years because of its excellent mechanical properties. These include high strength with good ductility, good wear resistance, fatigue strength and fracture toughness. It is therefore considered as an economical substitute for wrought or forged steel in several structural applications especially in the automotive industry. In this investigation, a nodular or ductile cast iron with predominantly pearlitic as-cast structure was processed by a novel two-step austempering process. Two batches of samples were prepared. All the specimens were initially austenitized at 927 °C (1700 °F) for 2 h. The first batch of samples were processed by conventional single-step austempering process at several temperatures such as 260 °C (500 °F), 273 °C (525 °F), 288 °C (550 °F), 302 °C (575 °F), 316 °C (600 °F), 330 °C (625 °F), 343 °C (650 °F), 357 °C (675 °F), 371 °C (700 °F), 385 °C (725 °F) and 400 °C (750 °F) for 2 h, whereas the second batch of samples were processed by the two-step austempering process. These samples were initially quenched for 5 min in a salt bath maintained at 260 °C (500 °F) and then austempered for 2 h at several austempering temperatures. These temperatures were 288 °C (550 °F), 302 °C (575 °F), 316 °C (600 °F), 330 °C (625 °F), 343 °C (650 °F), 357 °C (675 °F), 371 °C (700 °F), 385 °C (725 °F) and 400 °C (750 °F). Influence of this two-step austempering process on microstructure and mechanical properties of ADI was examined. Test results show that this two-step austempering process has resulted in significant improvement in yield and tensile strengths and fracture toughness of the material over the conventional single-step austempering process.