Self-Tension of Martensite during Constrained Transformation

2005 ◽  
Vol 475-479 ◽  
pp. 1937-1940 ◽  
Author(s):  
Li Shan Cui ◽  
Yan Jun Zheng
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
The Self ◽  
Experimental Results ◽  
Reverse Transformation ◽  
Transformation Temperatures ◽  
External Constraint

In a constrained martensitic transformation of shape memory alloys, a fraction of martensite is always retained in the materials. Experimental results showed that the remaining martensite could be plastically deformed by the generated recovery stresses. The self-tension process elevated the reverse transformation temperatures of the remaining martensite, and the external constraint conditions had no significant effect on the self-tension process of the remaining martensite.

Investigation of Ageing Phenomena in CuAlNi Based Shape Memory Alloys

2007 ◽  
Vol 537-538 ◽  
pp. 129-136 ◽  
Author(s):  
Marton Benke ◽  
Valéria Mertinger ◽  
E. Nagy ◽  
Jan Van Humbeeck
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Ternary Alloy ◽  
Room Temperature ◽  
Beta Phase ◽  
Heat Treatments ◽  
Thermoelastic Martensitic Transformation ◽  
Transformation Temperatures ◽  
Exothermic Process

The ageing phenomena and its effect on the thermoelastic martensitic transformation was investigated in three Cu-base SMAs. The transformation temperatures shifted to higher temperatures due to aging in the beta-phase. To increase the alloy’s ductility, a definite amount of Mn (4 wt%) and Fe (2 wt%) were added to the ternary alloy. The thermoelastic martensitic transformation was found in the not-aged samples of the CuAlNiMn and CuAlNiMnFe alloys. This transformation was destroyed due to ageing heat treatments by a fairly unknown exothermic process. The thermoelastic martensitic transformation appeared again in the aged CuAlNiMn and CuAlNiMnFe samples after keeping them on room temperature for a few months. This phenomena was investigated by DSC, SEM, TEM, and XRD.

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.

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.

High Temperature Shape Memory Alloys

1999 ◽  
Vol 121 (1) ◽  
pp. 98-101 ◽  
Author(s):  
Jan Van Humbeeck
Keyword(s):  
High Temperature ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Quality Standards ◽  
Reverse Transformation ◽  
Transformation Temperatures ◽  
Minimum Quality Standards ◽  
Functional Behavior ◽  
Minimum Quality ◽  
Alloy Systems

Several alloy systems can be selected for high-temperature shape memory alloys, defined as alloys with stable reverse transformation temperatures above 120°C. However, due to the lack of minimum quality standards for stability, ductility, functional behavior and reliability, no successful applications have been realized so far. Research on high temperature shape memory alloys (HTSMA) is, nevertheless, an important topic not only for scientific reasons but also due to the market pull. This paper reviews existing systems of HTSMA pointing out their weak and strong parts.

Effect of Aging on Microstructure and Martensitic Transformation in Ti-Zr-Ni Shape Memory Alloys

2007 ◽  
Vol 539-543 ◽  
pp. 3163-3168 ◽  
Author(s):  
Adrian Sandu ◽  
Koichi Tsuchiya ◽  
Shinya Yamamoto ◽  
Masayuki Tabuchi ◽  
Yoshikazu Todaka ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Martensitic Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Vickers Hardness ◽  
Isothermal Aging ◽  
Transformation Temperatures ◽  
Second Stage ◽  
Stage Process

Effect of isothermal aging on martensitic transformation temperatures, mechanical properties and microstructure was investigated for a Ni-rich Ti-Zr-Ni shape memory alloy at temperatures ranging from 673 K to 773 K. The aging behaviour was two stage process: the first stage associated with an increase in the Vickers hardness and a decrease in martensitic transformation temperatures and the second stage with a decrease in the hardness and increase in the transformation temperatures. Second stage was also characterized by the appearance of nano-scale precipitates, which has never been reported.

Effect of Aging on Phase Transition Behavior of Ti50Ni15Pd25Cu10 High Temperature Shape Memory Alloys

2015 ◽  
Vol 1101 ◽  
pp. 177-180 ◽  
Author(s):  
Saif Ur Rehman ◽  
Mushtaq Khan ◽  
Liaqat Ali ◽  
Syed Husain Imran Jaffery
Keyword(s):  
High Temperature ◽  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Martensite Phase ◽  
Two Stage ◽  
Transformation Temperatures ◽  
Transition Behavior ◽  
Forward Transformation ◽  
Niti Shape Memory Alloys

Formation of Ni4Ti3 precipitates during aging of Ni-rich binary NiTi shape memory alloys and its effect on transition behavior during transformation from austenite to martensite phase has been studied extensively. However for equi-atomic NiTi-based quaternary high temperature shape memory alloy, two-stage martensitic transformation was detected for the first time. The Ti50Ni15Pd25Cu10 high temperature shape memory alloys were investigated for the hardness and transformation temperatures at aging temperature of 550°C. Aging at 550°C for 6 h resulted in remarkable increase in the hardness, whereas the phase transformation temperatures decreased significantly. During forward transformation from austenite to martensite, two-stage martensitic transformation; B2 (cubic) → R-phase and R-phase → B19 (orthorhombic) was observed.

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