Characterization of Crystallographic Properties in the α→γ? martensitic transformation in a Fe-Mn-Al-Ni system by EBSD

C. SOBRERO; J. SIGNORELL; J. M. VALLEJOS; J. SIGNORELL; M. AVALOS

Darmstadt

Congreso; Materials Science and Engineering Congress 2018; 2018

FEMS - TMS

Electron Backscatter Diffraction (EBSD) is a very accurate and reliable tool forapproaching complex crystallographic problems. This technic can be employed forassessing the formation of phases during evolving material processes. It presents severaladvantages over other techniques commonly used in crystallography, such as TEM and Xray or neutron diffraction. In this work, we present the EBSD quantitative analysis for thedetermination of the orientation relationships between α parent phase and γ? productphase in the martensitic transformation in a Fe-Mn-Al-Ni system. For the first time, theα→γ? orientation relationship was experimentally well established. The Pitsch modelcaptures the transformation in more than 85% of the grains. By processing the EBSDmaps containing information about morphology, grain size and local lattice distortion wecould establish that the cases in which the Pitsch orientation relationship is not fulfilled aredue to the distortion of the crystalline lattice in the product phase due to accumulation ofdeformation during the martensitic transformation. We also demonstrate that the effect of alow value of input data spread does not severely affect the results obtained from averagevalues. This allows us to avoid a point-to-point study, much more computationallyexpensive. These results experimentally sustain that the transformation mechanism thatgoverns the martensitic transformation is the dislocation-based heterogeneous BogersBurgers and the number of possible martensite variants is twelve. By using thecrystallographic features of the Pitsch orientation relationship, the transformation strainsand stress-induced stress can be accurately calculated