Role of defects for the spontaneous vitrification ofβ-(Cr,Ti)

The high-temperature {β}-(Cr,Ti) solid solution can be retained on quenching to room temperature. This phase vitrifies spontaneously on subsequent annealing at a relatively low temperature depending on the degree of quenched-in disorder. We report on experiments that establish the decisive role of disorder in providing heterogeneous nucleation sites for the amorphous-phase growth. Different levels of defects were created in {β}-(Cr,Ti) by ion irradiation. The structural relaxation on subsequent annealing was then investigated by x-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. A direct relationship between the structural evolution and the defect concentration is inferred from the results. Further, the defects mediate a diffusion mode that seems to be coupled with vitrification.