Effects of partial crystallization in Pt-Si-B-based bulk metallic glasses on glass transition and crystallization of the remaining amorphous matrix

The influence of partial crystallization on the evolution of the characteristic temperatures, i.e. of the glass transition and the onset of crystallization, the density, and the mechanical properties of the bulk metallic glass Pt49.95Si6.4B24Ge3Cu16.65 is investigated. Partial crystallization is introduced by annealing the alloy in a stabilized salt bath at 350 °C and for different times and quantified by the residual heat of crystallization as measured in differential scanning calorimetry. It is found that the crystalline regions are enriched in platinum and the remaining amorphous phase is enriched in copper. The evolution of Tg and Tx of the remaining amorphous phase can be quantitatively linked to the degree of copper enrichment of the amorphous phase as crystallization advances. Hardness increases steadily with the degree of crystallization from 570 HV in the as-cast state to 750 HV in the fully crystallized state. In contrast, compressive strength drops steadily with increasing crystallinity due to increasing brittleness.