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

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.

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.

scholarly journals Microstructure and Phase Transformation Analysis of Ni50−xTi50Lax Shape Memory Alloys

Crystals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 345 ◽  
Author(s):  
Weiya Li ◽  
Chunwang Zhao
Keyword(s):  
Phase Transformation ◽  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Martensite Transformation ◽  
Transformation Behavior ◽  
Ni Content ◽  
Start Temperature

The microstructure and martensitic transformation behavior of Ni50−xTi50Lax (x = 0.1, 0.3, 0.5, 0.7) shape memory alloys were investigated experimentally. Results show that the microstructure of Ni50−xTi50Lax alloys consists of a near-equiatomic TiNi matrix, LaNi precipitates, and Ti2Ni precipitates. With increasing La content, the amounts of LaNi and Ti2Ni precipitates demonstrate an increasing tendency. The martensitic transformation start temperature increases gradually with increasing La content. The Ni content is mainly responsible for the change in martensite transformation behavior in Ni50−xTi50Lax alloys.

Transformation/Deformation Behavior and its Constitutive Equation for Ti-Ni-Cu Shape Memory Alloy

2008 ◽  
Vol 59 ◽  
pp. 129-134
Author(s):  
Yuji Takeda ◽  
Takaei Yamamoto ◽  
M. Uegaki ◽  
Hiroki Cho ◽  
Toshio Sakuma ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Constitutive Equation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Constitutive Equations ◽  
Deformation Behavior ◽  
Volume Fraction ◽  
Transformation Process ◽  
Reverse Transformation ◽  
Transformation Behavior

This paper describes the transformation and deformation behavior and its constitutive equation for Ti-41.7Ni-8.5Cu (at%) shape memory alloy. Plastic deformation after pre-deformation is investigated using the volume fraction of slip-deformed martensite. New kinetics and constitutive equations are proposed for the reverse transformation process. The material constants in the proposed equationa are determined from the results of tensile and heating/cooling tests of Ti-41.7Ni-8.5Cu (at%) shape memory alloy. The calculated results describe well the deformation and transformation behavior affected by pre-strain.

Spherical Indentation of Superelastic Shape Memory Alloys

2007 ◽  
Vol 334-335 ◽  
pp. 601-604
Author(s):  
Wen Yi Yan ◽  
Qing Ping Sun
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Bifurcation Point ◽  
Reverse Transformation ◽  
Spherical Indentation ◽  
Indentation Hardness ◽  
Characteristic Points ◽  
Forward Transformation ◽  
Transformation Stress ◽  
Return Point

Spherical indentation of superelastic shape memory alloys (SMAs) has been theoretically analyzed. Two characteristic points on the superelastic indentation curve have been discovered. The bifurcation force corresponding to the bifurcation point relies on the forward transformation stress and the return force corresponding to the return point relies on the reverse transformation stress. Based on these theoretical relationships, an approach to determine the transformation stresses of superelastic SMAs has been proposed. To improve the accuracy of the measurement, a slope method to locate the two characteristic points from the slope curves is further suggested. Additionally, the spherical indentation hardness was also analyzed.

Cooling rate effects on the structure and transformation behavior of Cu-Zn-Al shape memory alloys

2014 ◽  
Vol 21 (11) ◽  
pp. 1109-1114 ◽  
Author(s):  
Nicoleta-Monica Lohan ◽  
Marius-Gabriel Suru ◽  
Bogdan Pricop ◽  
Leandru-Gheorghe Bujoreanu
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Cooling Rate ◽  
Transformation Behavior ◽  
Rate Effects
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