Martensite and Reverse Transformation Temperatures of TiAu-Based and TiIr-Based Intermetallics

2021 ◽  
pp. 159399
Author(s):  
Mehrdad Zarinejad ◽  
Kiyohide Wada ◽  
Farshid Pahlevani ◽  
Reza Katal ◽  
Sajjad Rimaz
Keyword(s):  
Reverse Transformation ◽  
Transformation Temperatures

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.

scholarly journals Evaluation Methods for Non-contact Bend and Free Recovery Tests of Thin NiTi Wires and Their Effects on Measured Transformation Temperatures

2020 ◽  
Author(s):  
Jonathan Apell ◽  
Markus Rettenmayr ◽  
Andreas Undisz
Keyword(s):  
Evaluation Method ◽  
Evaluation Methods ◽  
Reverse Transformation ◽  
Two Stage ◽  
Fourth Degree ◽  
High Noise ◽  
Transformation Temperatures ◽  
Increased Sensitivity ◽  
Niti Wires ◽  
Shape Changes

Abstract Non-contact evaluation of transformation temperatures via bend and free recovery tests requires precise optical evaluation of shape changes of NiTi components. A variety of experimental setups is documented in the literature, but the influence of the evaluation method on the transformation temperatures is rarely assessed in detail. In the present work, the reverse transformation of bent wires is evaluated comparing the tracking of the lowest wire point and the tracking of the curvature. For calculating curvatures, different approaches of fitting the wire outline were applied. Fourth degree polynomials and ellipse segment fits were found to cause high noise toward the end of the reverse transformation, second degree polynomials and circle segment fits led to increased sensitivity in that region. Accordingly, the evaluation of curvature allowed to resolve a two-stage reverse transformation, which was otherwise obscured. The reasons for this effect are discussed comparing curvatures as determined by the different evaluation methods.

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 Strain Rates on the Transformation Behavior of Ni-Ti Alloy

2007 ◽  
Vol 539-543 ◽  
pp. 3231-3236
Author(s):  
Hidefumi Date
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Liquid Nitrogen ◽  
Testing Machine ◽  
Martensite Phase ◽  
Reverse Transformation ◽  
Strain Rates ◽  
Ti Alloy ◽  
Compressive Test ◽  
Transformation Temperatures

In order to clarify the effect of strain rates on phase transformation behaviors of Ni-Ti alloy, a compressive test using a cylindrical specimen of polycrystalline Ni-Ti alloy of Ti-50.69 at% Ni was carried out at a high strain rate and a low strain rate. The transformation temperatures were determined by a differential scanning calorimeter (DSC) using a sample cut from a compressed specimen. The transformation temperatures of the specimens before deformation were Ms= 303 K, Mf = 287 K, As = 297 K and Af = 319 K, respectively. The compressive test was carried out using specimen heated from liquid nitrogen temperature to room temperature. A universal testing machine as a static test apparatus and a Split Hopkinson Bar apparatus for a dynamic test were used. The specimen had a reoriented martensite phase after deformation because the superelastic effect was not observed upon unloading. Two reverse transformations during heating and a forward transformation during cooling were observed by DSC measurement. The first reverse transformation corresponds to that of thermal-induced martensite by immersion in liquid nitrogen and the second reverse transformation corresponds to that of reoriented martensite with slips in a polycrystalline matrix introduced by plastic deformation. The reverse transformation of the martensite phase with a slip exhibited strong strain rate dependency. Plastic strains and strain rate had strong influence on the shape recovery. The interaction between the temperature elevation by a conversion of plastic work and slip generated by dynamic plastic deformation is a complicated problem.

The stabilisation of step-quenched copper-zinc-aluminum martensite part I: The reverse transformation temperatures

1984 ◽  
Vol 18 (9) ◽  
pp. 893-898 ◽  
Author(s):  
Jan Van Humbeeck ◽  
Jan Janssen ◽  
Ngoie Mwamba ◽  
Luc Delaey
Keyword(s):  
Reverse Transformation ◽  
Transformation Temperatures ◽  
Copper Zinc

The effect of shock-wave loading on transformation temperatures, elastic and anelastic properties of β′ 1 Cu-Al-Ni martensitic single crystals

2002 ◽  
Vol 82 (12) ◽  
pp. 2419-2440
Author(s):  
S. Golyandin ◽  
S. Kustov ◽  
S. Nikanorov ◽  
K. Sapozhnikov ◽  
A. Sinani ◽  
...  
Keyword(s):  
Shock Wave ◽  
Single Crystals ◽  
Shock Wave Loading ◽  
Wave Loading ◽  
Transformation Temperatures

THE INFLUENCE OF HAEMOGLOBIN-S AND G6PD DEFICIENCY ON THE ACTIVITY OF THE 17β-HYDROXYSTEROID DEHYDROGENASE OF INTACT HUMAN ERYTHROCYTES

1974 ◽  
Vol 75 (4) ◽  
pp. 793-800
Author(s):  
A. O. Sogbesan ◽  
O. A. Dada ◽  
B. Kwaku Adadevoh
Keyword(s):  
Enzyme Activity ◽  
Dehydrogenase Activity ◽  
Sex Steroids ◽  
G6pd Deficiency ◽  
Incubation Medium ◽  
Hydroxysteroid Dehydrogenase ◽  
G6pd Activity ◽  
Reverse Transformation ◽  
Oxidative Transformation ◽  
Haemoglobin S

ABSTRACT The 17β-hydroxysteroid dehydrogenase activity in intact erythrocytes of Nigerian patients, in particular with regard to haemoglobin genotypes and G6PD* activity was studied. The G6PD activity of the erythrocyte did not affect the oxidative transformation of testosterone to androstenedione and of oestradiol to oestrone. The reduction (reverse transformation) was inhibited in G6PD-deficient erythrocytes but this inhibition was offset by the addition of 0.025 m glucose to the incubation medium. The per cent oxidation transformation of testosterone was higher in Hb-AA than in Hb-SS erythrocytes. It is suggested that the differences may be a result of either lower enzyme activity in the Hb-SS erythrocytes or of differences in the uptake and possibly binding of sex steroids by intact Hb-SS and Hb-AA erythrocytes.

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