Effects of alloying elements on the Snoek-type relaxation in Ti–Nb–X–O alloys (X = Al, Sn, Cr, and Mn)

The effect of alloying elements on the oxygen Snoek-type relaxation in the Ti–24Nb–X–1.7O alloys (X = 1Al, 2Al, 1Sn, 2Sn, 2Cr, 2Mn) was investigated in order to develop high damping materials based on point defect relaxation process. The relaxation strength of the Ti–Nb–Al–O and Ti–Nb–Sn–O alloys is the highest while that of the Ti–Nb–Mn–O and Ti–Nb–Cr–O alloys is the lowest. The dipole shape factor (δλ) and critical temperature Tc, which are intrinsic to the Snoek-type relaxation, were figured out and analyzed in terms of the d-orbital energy level (Md) for each alloy based on the measured damping peak. With the decreasing Md, the δλ increases and saturates at last when the Md decreases to a certain value (about 2.435 eV), while the critical temperature Tc decreases linearly. The parameter Md can be taken as a key parameter in designing high damping β-Ti alloys, that is, to design an intermediate value of Md at which the values of both δλ and Tc are as high as possible.