(2010) Aufrecht, Jochen Marc; Mittemeijer, Eric Jan (Prof. Dr. Ir.)
The polytypic transformations of the Laves phases in the Nb-Cr and the Hf-Cr system have been investigated by means of Differential thermal analysis (DTA), X-ray powder diffraction (XRPD), neutron diffraction (ND) and high-resolution electron microscopy (HRTEM). The interrelation between specific layer-stacking irregularities occuring in these phases and the polytypic phase transformations have been established. For Hf-Cr, a kinetical analysis based on XRPD data has been performed and the effective activation energy of the C14-to-C15 transformation has been obtained. For both systems, the constitution has been reinvestigated and in case of Nb-Cr, the absence of a stable hexagonal Laves-phase modification has been found.
