Rapid solidification and phase stability evaluation of Ti–Si–B alloys

Ti-rich Ti–Si–B alloys can be considered for structural applications at high temperatures (max. 700 °C), however, phase equilibria data is reported only for T = 1250 °C. Thus, in this work the phase stability of this system has been evaluated at 700 °C. In order to attain equilibrium conditions in shorter time, rapid solidified samples have been prepared and carefully characterized. The microstructural characterization of the produced materials were based on X-ray diffraction (XRD), scanning electron microscopy (SEM-BSE), high resolution transmission electron microscopy (HRTEM), High Temperature X-ray diffraction with Synchrotron radiation (XRDSR) and Differential Scanning Calorimetry (DSC). Amorphous and amorphous with embedded nanocrystals have been observed after rapid solidification from specific alloy compositions. The values of the crystallization temperature (Tx) of the alloys were in the 509–647 °C temperature range. After Differential Scanning Calorimetry and High Temperature X-ray Diffraction with Synchrotron radiation, the alloys showed crystalline and basically formed by two or three of the following phases: αTi, Ti6Si2B; Ti5Si3; Ti3Si and TiB. It has been shown the stability of the Ti3Si and Ti6Si2B phases at 700 °C and the proposition of an isothermal section at this temperature.

Research highlights
► Rapid solidification of Ti-rich Ti–Si–B alloys promoted significant refinement of the microstructures.
► Amorphous and amorphous with embedded nanocrystals have been observed after rapid solidification from specific alloy compositions.
► The values of the crystallization temperature (Tx) of the alloys were in the 509–647 °C temperature range.
► After Differential Scanning Calorimetry and High Temperature X-ray diffraction with synchrotron radiation, the alloys showed crystalline and basically formed by two or three of the following phases: αTi, Ti6Si2B; Ti5Si3; Ti3Si and TiB.
► It has been shown the stability of the Ti3Si and Ti6Si2B phases at 700 °C and the proposition of an isothermal section at this temperature.