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

等温淬火球墨铸铁(ADI)是一种经多道工序热处理的铸铁材料。这样就形成了一种叫做奥铁素体的显微组织，它由亚稳的残余奥氏体层、铁素体片层和球状石墨组成。这种显微组织是ADI具有比初始状态更好的力学性能的原因。从用于板材成形的TRIP钢中得知，亚稳残余奥氏体会在外加载荷下转变为马氏体。基于DFG研究项目的结果，将用中子衍射法原位研究选定的ADI材料在热处理过程中的相变动力学。根据不同的热处理参数，将确定残余奥氏体相组成和碳含量，以及显微组织和力学性能。在拉伸和压缩试验中，将使用中子衍射法原位测量热处理样品中马氏体的形成。实验数据将用于检验现有的计算TRIP钢中马氏体应力和应变诱导形成的数学模型。这些模型将经过验证和扩展，以便可以用于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.