Effect of Doping with р-Elements (Al, Si, Ge, Sn) and Zirconium on the Structure and Properties of Titanium-Boride Eutectic Alloys

Abstract

The influence of silicon, germanium, tin (X), and aluminum on the structure, physicochemical and mechanical properties of ternary Ti–B–X and Ti–Al–B (5 and 7.5 at.% B) and quaternary Ti–Al–B–X and Ti–Zr–Al–В (9 at.% Al and 5 at.% B; 8.5 at.% Al and 7.5 at.% B) alloys is investigated by metallography, scanning electron microscopy (SEM), X-ray diffraction, differential thermal analysis (DTA), microhardness measurement, Vickers hardness measurement (from room temperature to 900 °C), bending tests (room temperature), and compression tests (from room temperature to 700 °C). The alloys are melted in an arc furnace from pure materials. Doping with p-elements (Al, Si, Ge, and Sn) does not change the specific titanium-boride eutectic structure in the two-phase (Ti) + TiB field. The doping additions hardly change the chemical composition of the eutectic and only decrease the boron content by 1–2 at.%. P-elements Al, Si, Ge, and Sn are not soluble in titanium borides TiB and completely concentrate in the metal matrix in two-phase (Ti) + TiB alloys. For the doped two-phase (Ti) + TiB alloys, the temperature of incipient sharp softening is shown to be exclusively connected with the matrix composition. All the above-mentioned alloying additions increase the hardness and strength of titanium-boride eutectic alloys in the entire temperature range of interest and increase the temperature of incipient sharp softening from 500 to 600–650 °C.