The Effect of Hafnium and Thermal Cycling on the Transformation Temperatures of NiTi-Based Shape Memory Alloys

1999 ◽  
Vol 604 ◽  
Author(s):  
Paul E. Thoma ◽  
John J. Boehm
Keyword(s):  
Shape Memory Alloys ◽  
Thermal Cycling ◽  
Shape Memory ◽  
Phase Transformations ◽  
Niti Alloy ◽  
Thermal Cycles ◽  
Transformation Temperatures

AbstractThe effect of thermal cycling on the austenite to martensite (A→M) and martensite to austenite (M→A) transformation temperatures (TTs) of Ni49.8Ti50.2 and Ni49.8Ti40.2Hf10 shape memory alloys is investigated. Test specimens are from arc melted buttons homogenized at 900°C for 100 hours. Results show that the A→M and M→A TTs for the alloys decrease with increasing number of thermal cycles through the phase transformations. The A→M TT of the NiTiHf alloy stabilizes more quickly than the A→M TT of the NiTi alloy when cycled. However, the M→A TT of the binary NiTi alloy stabilizes more quickly than the M→A TT of the NiTiHf alloy when cycled.

scholarly journals Effect of Stoichiometry on Shape Memory Properties and Functional Stability of Ti–Ni–Pd Alloys

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 798 ◽  
Author(s):  
Yuki Hattori ◽  
Takahiro Taguchi ◽  
Hee Kim ◽  
Shuichi Miyazaki
Keyword(s):  
High Temperature ◽  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Thermal Cycling ◽  
Shape Memory ◽  
Stoichiometric Composition ◽  
Atomic Ratio ◽  
Transformation Temperatures ◽  
Shape Memory Properties ◽  
Ti Content

Ti–Ni–Pd shape memory alloys are promising candidates for high-temperature actuators operating at above 373 K. One of the key issues in developing high-temperature shape memory alloys is the degradation of shape memory properties and dimensional stabilities because plastic deformation becomes more pronounced at higher working temperature ranges. In this study, the effect of the Ti:(Ni + Pd) atomic ratio in TixNi70−xPd30 alloys with Ti content in the range from 49 at.% to 52 at.% on the martensitic transformation temperatures, microstructures and shape memory properties during thermal cycling under constant stresses were investigated. The martensitic transformation temperatures decreased with increasing or decreasing Ti content from the stoichiometric composition. In both Ti-rich and Ti-lean alloys, the transformation temperatures decreased during thermal cycling and the degree of decrease in the transformation temperatures became more pronounced as the composition of the alloy departed from the stoichiometric composition. Ti2Pd and P phases were formed during thermal cycling in Ti-rich and Ti-lean alloys, respectively. Both Ti-rich and Ti-lean alloys exhibited superior dimensional stabilities and excellent shape memory properties with higher recovery ratio and larger work output during thermal cycling under constant stresses when compared with the alloys with near-stoichiometric composition.

Phase Transformations of Ferromagnetic Fe-Pd-Pt-Based Shape Memory Alloys

2003 ◽  
Vol 785 ◽  
Author(s):  
Gwon-seung Yang ◽  
Reid Jonasson ◽  
Seung-nam Baek ◽  
Kinzo Murata ◽  
Shozo Inoue ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Phase Transformations ◽  
Treatment Time ◽  
Heat Treatment Time ◽  
Induction Melting ◽  
Ferromagnetic Shape Memory Alloys ◽  
Transformation Temperatures ◽  
First Order

ABSTRACTSeveral ternary Fe-Pt-Pd alloys with the compositions of Fe-(25-x) at% Pt-x at% Pd and Fe-y at% Pt-(30-y) at% Pd were investigated to study their phase transformations in order to develop ductile ferromagnetic shape memory alloys appearing around room temperature. Alloys were prepared by vacuum floating induction melting, followed by hot rolling at 1000°C and homogenization at 900° C. Homogenized alloys were heat treated at 650°C for various periods of time in vacuum for atomic ordering in encapsulated quartz tubes, and quenched into iced water. It was found that in general the transformation temperatures changes with heat treatment time. In the case of Fe-23at.%Pt-2at.%Pd, Ms temperature increased and the difference between Ms and Mf increased with increasing heat treatment time, which was different from Fe3Pt where a degree of order becomes one. As heat treatment time increased, there was a tendency in that a strong first-order transformation in the disordered state was replaced by a weak first-order transformation. The Curie temperature of the alloys rose drastically with the addition of Pd, along with the transformation temperatures. Fe-23at.%Pt-2at.%Pd showed good shape memory effect after 8 hours of heat treatment at 650°C. This alloy showed much better shape recovery than any other binary Fe-Pt and Fe-Pd shape memory alloys.

Thermal cycling effects in high temperature Cu–Al–Ni–Mn–B shape memory alloys

1997 ◽  
Vol 12 (9) ◽  
pp. 2288-2297 ◽  
Author(s):  
J. Font ◽  
J. Muntasell ◽  
J. Pons ◽  
E. Cesari
Keyword(s):  
High Temperature ◽  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Thermal Cycling ◽  
Shape Memory ◽  
Parent Phase ◽  
Aluminum Boride ◽  
Transformation Temperatures ◽  
Dsc Measurements ◽  
Number Of Cycles

The effects of thermal cycling through the martensitic transformation have been studied in three Cu–Al–Ni–Mn–B high temperature shape memory alloys. An increase of the martensitic transformation temperatures with the number of cycles (up to ∼7 K after 60 cycles) has been generally observed by DSC measurements. The microstructure of these alloys is rather complicated, with the presence of big manganese or aluminum boride particles and small boron precipitates, as well as the formation of dislocations during thermal cycling. By means of aging experiments, it has been shown that the evolution of transformation temperatures during cycling is mainly due to the step-by-step aging in parent phase accompanying the thermal cycling, and that the dislocations formed during cycling have only a very small effect, at least up to 60 cycles.

Influence of Cu addition on transformation temperatures and thermal stability of TiNiPd high temperature shape memory alloys

2017 ◽  
Vol 233 (5) ◽  
pp. 800-808
Author(s):  
Saif ur Rehman ◽  
Mushtaq Khan ◽  
A Nusair Khan ◽  
Khurshid Alam ◽  
Syed Husain Imran Jaffery ◽  
...  
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Shape Memory Alloys ◽  
Thermal Cycling ◽  
Shape Memory ◽  
Thermal Hysteresis ◽  
Transformation Temperatures ◽  
Cu Content ◽  
Positive Effect ◽  
Thermal Stability Of

In this research, four high temperature shape memory alloys, Ti50Ni25-xPd25Cux (x = 0, 5, 10 and 15) were developed and designated 0Cu, 5 Cu, 10 Cu, and 15Cu, respectively. The effect of 5%, 10%, and 15% (all in atomic percent) Cu addition was investigated through their microstructure analysis, transformation temperatures and thermal stability. After the alloying of Cu content in their desired percentage, the alloys were named as 0Cu, 5Cu, 10Cu and 15Cu alloys. The martensite onset temperature Ms of ternary 0Cu alloy increased by 12.5 ℃, 27.5 ℃ and 60.5 ℃, respectively, by replacement of Ni with 5%, 10% and 15% Cu. Similarly, the austenite finish temperature Af increased by 11 ℃, 25 ℃, and 52 ℃, respectively. At the same time, thermal hysteresis of the 5Cu, 10Cu, and 15Cu alloys decreased by 1.5 ℃, 2.5 ℃, and 8.5 ℃, respectively, as compared to 0Cu alloy. The thermal stability of ternary 0Cu alloy was improved by replacing Ni with Cu. During thermal cycling, the net drop in Ms and Af of 0Cu alloy was 7.5 ℃ and 14 ℃, respectively. By replacing Ni with 5%, 10%, and 15% Cu, the net drop in Ms decreased to 5 ℃, 3.7 ℃, and 3 ℃, respectively, whereas the net drop in Af decreased to 10 ℃, 8.7 ℃, and 5 ℃. The overall results suggested that by the addition of 5%, 10%, and 15% Cu in place of Ni in TiNiPd alloys, the transformation temperatures and thermal stability improved. At the same time, thermal hysteresis decreased to a reasonable level which has a positive effect on the actuation behavior.

scholarly journals Effect of Ni-Content on the Transformation Temperatures in NiTi-20 at. % Zr High Temperature Shape Memory Alloys

Metals ◽  
2017 ◽  
Vol 7 (11) ◽  
pp. 511 ◽  
Author(s):  
Matthew Carl ◽  
Jesse Smith ◽  
Brian Van Doren ◽  
Marcus Young
Keyword(s):  
High Temperature ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Transformation Temperatures ◽  
Ni Content
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