Use of EBSD Technique as a Means to Investigate the Microstructure of Engineering Materials

Doktorsavhandling, 2005

Abstract Materials Science and Engineering has the aim to design or engineer the structure of a material to produce a predetermined set of properties. To be able to understand and predict the properties and observable characteristics of engineering materials, it is therefore necessary to understand their microstructure. With the evolution of new measuring techniques, the range of obtainable information is usually extended, i.e. materials features can be investigated which were not accessible before and/or the data can be obtained easier or in a statistical more significant amount. This work was executed with the aim to provide knowledge on to which extent the electron backscatter diffraction technique, a relatively new method in the field of electron microscopy, can be used to characterise engineering materials. Hence, the study includes investigations of three different types of materials such as WC-Co composite, Co-Cr-Mo laser clad, and coronary artery stents respectively thin steel wires, and describes conventional as well as more dedicated EBSD work. EBSD was able to provide statistical information on the occurrence of special boundaries in WC-Co composites. Furthermore, it could be shown that the frequency of occurrence of Σ2 boundaries in the composite is not affected by the Co content (the binder phase). Combined with TEM investigations and ab initio calculations, EBSD could provide a better understanding of the deformation behaviour of WC-Co composites. The example of Co-Cr-Mo clad has shown that by combining EBSD and EDX analysis, a complete overview of the microstructure is obtained. It has also been shown that the EBSD technique is an effective tool for investigating the microstructure evolution during deformation and for describing the microstructure–mechanical properties relationship. EBSD was also applied to materials with oligocrystalline structures (coronary stents/thin steel wires). The preliminary results on the thin wires have shown that it is possible to perform deformation series experiments and to obtain useful orientation data on individual grains.