In-Situ Measurement of Deformation Induced Formation of Martensite in Austempered Ductile Iron (ADI)

等温球墨铸铁（ADI）是一种经过多阶段热处理的铸铁材料。这样就形成了一种叫做奥铁素体的微观结构，由亚稳残余奥氏体、铁素体束和球状石墨组成。这种微观结构是ADI相对于初始状态具有优异力学性能的原因。从用于钣金成形工艺的trip钢中，我们知道亚稳态残余奥氏体在外部载荷作用下可以转变为马氏体。基于DFG研究项目的结果，将利用中子衍射对选定的adi材料在热处理过程中的相变动力学进行原位研究。根据各自的热处理参数，将确定残余奥氏体的相组成和碳含量以及显微组织和机械材料性能。热处理试样马氏体的形成将在拉伸和压缩试验中使用中子衍射进行原位测量。实验数据将用于测试用于计算trip钢中应力和应变诱导马氏体形成的现有数学模型。将对这些模型进行验证和扩展，以便它们可以用于ADI。

Austempered Ductile Iron (ADI) is a cast iron material which is heat-treated in a multistage process. Thus a microstructure called ausferrite forms, consisting of metastable retained austenite, ferrite sheaves and spheroidal graphite. This microstructure is the reason for the excellent mechanical properties of ADI compared to the initial state. From TRIP-steels, which are used in sheet metal forming processes, it is known that metastable retained austenite can transform to martensite under external loads.Based on the results of the DFG research project the phase transformation kinetics of selected ADI-materials during the heat treatment will be investigated in-situ using neutron diffraction. The phase compositions and the carbon contents of the retained austenite will be determined together with the microstructures and mechanical material properties depending on the respective heat treatment parameters.The formation of martensite in heat-treated specimens will be measured in-situ using neutron diffraction during tension and compression tests. The experimental data will be used for testing existing mathematical models for calculation of stress and strain-induced formation of martensite in TRIP-steels. These models will be validated and extended so that they can be used for ADI.