Martensitic transformations, thermal expansion and mechanical properties of titanium-niobium alloys

Thermal expansion in quenched and cold rolled Ti-Nb alloys (30–50 w.% Nb) was studied and temperature ranges were determined, in which anomalies associated with the sample expansion and compression occur. Phase transformations were studied by means of X-ray diffraction in the temperature range $-190 <{\rm T} < +150^\circ$C. Cold rolling results in significant decrease of thermal expansion along the rolling direction. Thermal coefficient of linear expansion varies with niobium content for deformed alloys assuming negative values for alloys with 34–38% Nb the minimum value being $-1.3\cdot10^{-5}$ K$^{-1}$. Anomalies of TCLE are connected to temperature dependences of lattice constants of orthorhombic martensite, volume fractions ofthe phases and texture of the alloys