Frottement Intérieur Et Microdéformation Dans Les Transformations Martensitiques

Ti 51 Ni 39 Cu 10 SMA is more suitable than Ti 50 Ni 50 SMA for use as a high damping alloy at room temperature because it has higher inherent internal friction and wider martensitic transformation temperature range. Experimental results show that tan values of both (IF PT +IF I ) B2!B19 and (IF PT +IF I ) B19!B19 0 of Ti 51 Ni 39 Cu 10 SMA are linearly proportional to 0 = 1=2 when the applied and 0 are within 10 Hz and 15 mm, respectively. Since defects and dislocations pin the martensite twin boundaries and obstruct their mobility, it is important to prevent the introduction of defects or dislocations into the solution-treated Ti 51 Ni 39 Cu 10 SMA to maintain its high inherent internal friction.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Inherent Internal Friction of Ti51Ni39Cu10 Shape Memory Alloy

Chang

2007

“…1 and 4, their peak heights are nearly the same for the Ti 49:8 Ni 50:2 specimens with 1-100 thermal cycles. This indicates that the thermal-cycling induced dislocations will not conspicuously affect the martensitic transformation rate, 14) although they have significant effect on the martensitic transformation temperatures.…”

Section: The Characteristics Of the Relaxation Peak P Rmentioning

confidence: 94%

A Study on the Low Temperature Internal Friction Relaxation Peak in a Ti49.8Ni50.2 Alloy

Lin

Chou³

2006

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 .

“…The IF Tr term denotes transient internal friction and is much more significant than the IF PT and IF I terms during martensitic transformation. Delorme et al 22) pointed out that, during martensitic transformation in Fe-Ni, Co-Ni, and FeCr-Ni alloys, the IF Tr term is proportional to the cooling/ heating rate, the transformed volume rate, the applied frequency, and the strain amplitude, but it vanishes under the isothermal condition. 23) Most damping materials are used at constant temperature, so the damping capacities, i.e., the IF PT …”

Section: Introductionmentioning

confidence: 99%

Damping Capacities of Ti50Ni50−xCux Shape Memory Alloys Measured under Temperature, Strain, and Frequency Sweeps

Chien

Chang

2015

The damping capacities of Ti 50 Ni 50¹x Cu x SMAs with x = 0³20 at% were measured by DMA under temperature, strain and frequency sweep tests. The tan ¤ value exhibited at B2¼B19 transformation is significantly higher than that at B2¼B19A transformation under temperature/strain sweep tests. In the strain sweep test, the tan ¤ value decreases as the frequency increases, but it increases as the applied strain increases. The tan ¤ curves of the strain sweep tests can be fitted by tan ¤ = K¾ n with n values being close to the friction type model. Adding Cu enhances the tan ¤ values of both B19 martensite and B2¼B19 transformation in 0.1³10 Hz, but that of B19A martensite is enhanced only at 10 Hz. From 0.1 Hz to 1 Hz, the decrement of the tan ¤ value in IF I term is greater than that in IF PT term for SMA with x ² 5 at%. In the frequency sweep test, the tan ¤ value increases as the x value increases under the same applied frequency, no matter whether the martensite is B19A or B19.