Micro-Magnetic, Multiple-Parameter, Microstructure and Stress Analysis - 3MA - For Non-Destructive Material Properties Determination and Ageing Prediction

3MA is a multiple parameter modelling of mechanical and technological material properties. It is based on multiple regression and neural network algorithms which are calibrated by non-destructively (nd) determined data. These are selected from well-defined calibration specimens and by the use of different micro-magnetic nd-techniques (ndt). Magnetic domain walls (Bloch walls) move in the ferromagnetic materials under dynamic magnetisation. They strongly interact with microstructure parameters like dissolved atoms (C, N, Cu), Dislocations, precipitates, second phases and grain boundaries. All of the micro-magnetic techniques and derived paramters are based on these Bloch wall interactions. Therefore, they show interrelationships to mechanical parameters characterising strengthening or softening of the materials. The same type of microstructures ('lattice defects') impeding dislocation movement under mechancial load impedes Bloch wall movement under magnetic load. These mechanical parameters are hardness and those derived from the standard tensile test, like yield strength and tensile strength but also toughness-sensitve properties like the upper shelf value of the charpy-notch impact test and the fracture appearance transition temperature. The emphasis of the contribution is to discuss the 3MA methodology. The special material and microstructure propsed in the AMES-network for the round robin test, documenting material ageing after annealing and quenching, is only one example of a wider ranging application potential. 3MA is the official acronym for the development of ndt-techniques for materials property determination and prediction under the framework of the German Nuclear SafetyResearch Programme (Deimel et al., 1991).