The Effect of Reverse Transformation on Recovery • Recrystallization Process in Ti-Pd-Ni High Temperature Shape Memory Alloys

1996 ◽  
Vol 459 ◽  
Author(s):  
Ya Xu ◽  
Kazuhiro Otsuka ◽  
Tatsuhiko Ueki ◽  
Kengo Mitose
Keyword(s):  
High Temperature ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Parent Phase ◽  
Hardness Test ◽  
Reverse Transformation ◽  
Atomic Diffusion ◽  
Recrystallization Process ◽  
Scanning Calorimetry ◽  
Heating Treatment

ABSTRACTThe effect of martensitic reverse transformation on recovery • recrystallization process in cold rolled Ti-Pd-Ni high temperature shape memory alloys has been investigated systematically by flash heating treatment, micro-Vickers hardness test, differential scanning calorimetry and transmission electron microscopy. It was found that the temperatures of softening in hardness after flash heating treatments agree well with the reverse transformation temperatures in the present alloys, and most of the softening occurs within 60 seconds when annealing temperature is raised to above the reverse transformation temperature. We conclude that the recovery • recrystallization process is controlled by the reverse transformation. The reasons are considered based on the large difference in atomic diffusion rate in the parent phase and in the martensite.

Aging Effects of Cu-Zn-Al Shape Memory Alloys Studied by the Alchemi Measurements

1991 ◽  
Vol 246 ◽  
Author(s):  
K. Shimizu ◽  
Y. Nakata ◽  
O. Yamamoto
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Parent Phase ◽  
Stacking Faults ◽  
Martensite Phase ◽  
Reverse Transformation ◽  
Aging Effects ◽  
Scanning Calorimetry ◽  
Martensite Stabilization ◽  
Cu And Zn

AbstractThe aging effects of two kinds of Cu-Zn-Al shape memory alloys (Cu-ll.4 Zn-18.7A1 (A) and Cu-ll.2Zn-17.lAl (B) in at%) have been examined by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and atom location by channeling enhanced microanalysis (ALCHEMI). In the directly quenched (D.Q.) state, alloy A was the parent phase, Ms being 253 K, and alloy B was the martensite phase. The alloy B was subjected another quenching treatment as follows: It was once quenched into an oil bath at 423 K and held for 300 s, followed by quenching into iced water (step quench (S.Q.) ). The D.Q. alloy B did not exhibit the reverse transformation because of a stabilization of the martensbite phase, but the S.Q. alloy B did and its As temperature of the reverse transformation was raised with the progress of aging at the martensitic state. Fraction of Zn atoms at the Cu(2) site examined by the ALCHEMI measurements was almost the same in the parent phase of D.Q. alloy A and its aged one, indicating no change in Cu and Zn atom sites, while it was gradually decreased in S.Q. alloy B with the progress of aging. The fraction of Zn atoms in D.Q. alloy B was much lower than those in the S.Q. alloy B and its aged one. TEM observation of the S.Q. alloy B revealed that stacking faults as the lattice invariant shear in the M18R martensites decreased in the density with the progress of aging. The decrease in the fraction of Zn atoms and in the density of stacking faults well corresponds to the increase in As temperature, and thus the martensite stabilization was attributed to a disordering between Cu and Zn atoms and to an annihilation of stacking faults.

Reverse transformation behavior of TiNi shape memory alloys prestrained in the parent phase

2006 ◽  
Vol 21 (3) ◽  
pp. 26-28
Author(s):  
Huai Limin ◽  
Cui Lishan ◽  
Zhang Yaibin ◽  
Zheng Yanjun ◽  
Han Xiangli
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Parent Phase ◽  
Reverse Transformation ◽  
Transformation Behavior

The Role of Twinned and Detwinned Structures on Memory Behaviour of Shape Memory Alloys

2015 ◽  
Vol 1105 ◽  
pp. 78-82 ◽  
Author(s):  
Osman Adiguzel
Keyword(s):  
High Temperature ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Parent Phase ◽  
Martensitic Transformations ◽  
Phase Region ◽  
Finish Temperature ◽  
Β Phase

Shape memory alloys have a peculiar property to return to a previously defined shape or dimension when they are subjected to variation of temperature. Shape memory effect is facilitated by martensitic transformation governed by changes in the crystalline structure of the material. Martensitic transformations are first order lattice-distorting phase transformations and occur with the cooperative movement of atoms by means of lattice invariant shears in the materials on cooling from high temperature parent phase region. The material cycles between the deformed and original shapes on cooling and heating in reversible shape memory effect. Thermal induced martensite occurs as twinned martensite, and the twinned martensite structures turn into detwinned structures by deforming the material in the martensitic condition. Deformation of shape memory alloys in martensitic state proceeds through a martensite variant reorientation. The deformed material recovers the original shape on first heating over the austenite finish temperature in reversible and irreversible shape memory cases. Meanwhile, the parent phase structure returns to the twinned structure in irreversible shape memory effect on cooling below to martensite finish temperature and to the detwinned structure in reversible shape memory effect. Therefore, the twinning and detwinning processes have great importance in the shape memory behaviour of the materials. Copper based alloys exhibit this property in metastable β-phase region, which has bcc-based structures at high temperature parent phase field, and these structures martensitically turn into layered complex structures with lattice twinning following two ordered reactions on cooling.

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.

scholarly journals Application of in-situ nano-scanning calorimetry and X-ray diffraction to characterize Ni–Ti–Hf high-temperature shape memory alloys

2015 ◽  
Vol 603 ◽  
pp. 53-62 ◽  
Author(s):  
Patrick J. McCluskey ◽  
Kechao Xiao ◽  
John M. Gregoire ◽  
Darren Dale ◽  
Joost J. Vlassak
Keyword(s):  
High Temperature ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray

Effects of training on the thermomechanical behavior of NiTiHf and NiTiZr high temperature shape memory alloys

2020 ◽  
Vol 794 ◽  
pp. 139857 ◽  
Author(s):  
O. Karakoc ◽  
K.C. Atli ◽  
A. Evirgen ◽  
J. Pons ◽  
R. Santamarta ◽  
...  
Keyword(s):  
High Temperature ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Thermomechanical 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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