Nature and Regularities of the Orthorhombic α″-Phase Formation in Binary Titanium Alloys

A systematic study of the phase composition of quenched binary titanium alloys with d-metals of groups 5–11 from periods four to six was carried out using the methods of X-ray diffraction analysis. It was found that the formation of the orthorhombic α″-phase depends on the position of the alloying metal in the periodic table. The formation of the α″-phase occurs only in the systems Ti-V, Ti-Nb, Ti-Mo, Ti-Ru, Ti-Ta, Ti-W, Ti-Re, Ti-Os and Ti-Ir, and in other systems, it does not occur. It was found that the critical parameter for the formation of the α″-phase is the difference in the size of titanium atoms and those of the alloying metal {(rTi − rMe)/rTi 100%}. The formation of the α″-phase occurs only in systems where this value is lower than 9 at.%