A Study on the Low Temperature Internal Friction Relaxation Peak in a Ti<SUB>49.8</SUB>Ni<SUB>50.2</SUB> Alloy

Abstract

The low temperature relaxation peak appearing around 200 K in Ti 49:8 Ni 50:2 shape memory alloy is a multiple relaxation process with activation energy Q ¼ 0:39 eV and frequency factor f 0 ¼ 6:2 Â 10 9 s À1 and is associated with the interaction of dislocations with pinning vacancies. Due to the increase of dislocation density and the annihilation of quenched-in vacancies after thermal cycling, the height of relaxation peak P R decreases with increasing the number of thermal cycling. Higher amounts of dislocation-vacancy reaction cause a higher relaxation damping under the condition of higher quenching temperature. The quenched-in vacancies can have a significant effect on the transformation rate, and thus the heights of transformation peaks P H1 and P C1 decrease with increasing quenching temperature. Dislocations introduced by both thermal cycling and quenching from high temperature will depress the martensitic transformation, and hence decrease the peak temperatures of P H1 and P C1 .

Damping characteristics of Ti50Ni47Fe3 alloy

“…Hasiguti and Iwasaki [1] first reported a high IF peak in TiNi and since then many works have been reported on IF of TiNibased alloys [2][3][4][5][6][7][8][9][10][11][12][13][14]. A binary alloy of TiNi shows a very sharp IF peak near the martensitic transformation temperature, which is accompanied by an evident rigidity drop, and also another IF peak at around 200 K (usually called "200 K peak").…”

On the production and properties of novel particulate NiTip/AA2124 metal matrix composites

“…The temperature evolution of the frequency, which is related to the shear modulus of the sample (f ∼ √ G), decreases with increasing temperature, showing a clear minimum for P A → R and P M → A , characteristic of a phase transformation. Previous literature, suggest that peak P Rel is associated to the thermally activated movement of twin-related dislocations pinned by point defects (vacancies or Ti 3 Ni 4 ) in the martensite or R-phase inside NiTi particulates [9] rather than a process originated at the interface matrix/reinforcement [10]. figure.…”

Comparison of the two relaxation peaks in the Ti50Ni48Fe2 alloy

“…The relaxation behavior in shape memory alloys has been widely explored over the past decades [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Several speculations were proposed to interpret the relaxation peak.…”

“…Several speculations were proposed to interpret the relaxation peak. Dislocation relaxation [3] or dislocations-point defect (vacancies) interaction [4][5][6]16] was the most popular speculation in the past, since dislocations and vacancies unavoidably exist in these alloys. Twin boundaries relaxation under external stress was another prevailing speculation, since the relaxation peak was always observed in the martensitic state, in which twin boundaries are abundant [1,7].…”