Precipitation behavior of a CuAlNi shape memory alloy at elevated temperatures

1985 ◽  
Vol 19 (2) ◽  
pp. 231-234 ◽  
Author(s):  
Jogender Singh ◽  
Haydn Chen ◽  
C.M. Wayman
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Elevated Temperatures ◽  
Precipitation Behavior

Thermomechanical effects on phase transformations in single-crystal Cu–Al–Ni shape-memory alloy

2007 ◽  
Vol 22 (4) ◽  
pp. 994-1003 ◽  
Author(s):  
H.-S. Zhang ◽  
K. Komvopoulos
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Single Crystal ◽  
Shape Memory ◽  
Elevated Temperatures ◽  
Czochralski Method ◽  
Tensile Tests ◽  
Transformation Temperatures ◽  
Experimental Findings ◽  
Cyclic Straining

Single-crystal rods of Cu–Al–Ni shape-memory alloy fabricated from a molten pool of 82 wt% Cu, 14 wt% Al, and 4 wt% Ni by the Czochralski method were first heated to ∼870 °C and then quenched to obtain austenitic microstructures. Various microanalysis techniques were used to determine the chemical composition, microstructure, and phase-transformation temperatures of the produced alloy. Cyclic tensile tests with in situ temperature control demonstrated the occurrence of pseudoelastic deformation at elevated and close to phase-transformation temperatures and provided insight into the temperature dependence of the phase-transformation stress, damping characteristics, and cyclic straining of single-crystal Cu–Al–Ni alloy. The stress hysteresis observed in the pseudoelastic deformation cycles decreased at elevated temperatures. The stress response at different temperatures is associated with the formation, growth, and coalescence of martensite variants. Stress-induced phase-transformation mechanisms, coalescence of twin variants, and energy dissipation by pseudoelastic deformation are discussed in the context of experimental findings. The results illustrate the potential of single-crystal Cu–Al–Ni as a structural material for dynamic microsystems and temperature sensors.

Tension - Compression Asymmetry in Co49Ni21Ga30 High-Temperature Shape Memory Alloy Single Crystals

2013 ◽  
Vol 738-739 ◽  
pp. 82-86 ◽  
Author(s):  
Thomas Niendorf ◽  
Jayaram Dadda ◽  
Jan Lackmann ◽  
James A. Monroe ◽  
Ibrahim Karaman ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Stress State ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Single Crystals ◽  
Stress Level ◽  
Elevated Temperatures ◽  
Stress States ◽  
Tension Compression Asymmetry

This paper reports on the tension-compression asymmetry of [001]-oriented Co49Ni21Ga30 single crystals at elevated temperatures. Maximum strains of -4.8 % and 8.6 % in compression and tension, respectively, were found. A linear Clausius-Clapeyron relationship was observed for both stress-states where the smaller slope in tension resulted in a significant increase of the phase transformation temperatures with stress, which reached 180 °C under a constant stress level of 150 MPa. In addition, the material demonstrated a large pseudoelastic temperature range of about 300 °C under both stress state conditions. The results in this study unequivocally indicate the potential of these alloys for applications where elevated temperatures and stress levels prevail.

Thermal Behavior of Clay/Epoxy Nanocomposites

2012 ◽  
Vol 21 ◽  
pp. 23-28
Author(s):  
Artur S.C. Leal ◽  
Carlos José de Araújo ◽  
Suédina Maria L. Silva ◽  
Antônio Gilson Barbosa de Lima
Keyword(s):  
Thermal Stability ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Elevated Temperatures ◽  
Mechanical Analysis ◽  
Diglycidyl Ether ◽  
X Ray Diffraction ◽  
Curing Conditions ◽  
The Matrix ◽  
Epoxy Systems

In this work, the effect of curing agent, curing conditions and the incorporation of small amounts of organoclay on the thermal properties of DGEBA (diglycidyl ether of bisphenol A) epoxy resin was evaluated in order to develop an epoxy system for application as the matrix in active composites whose dispersed phase consists of shape memory alloy wires. The DGEBA resin was prepared using three amine derivatives as hardeners (triethylenetetramine - TETA, diethylenetriamine - DETA and diaminodiphenylsulfone - DDS) under varied curing conditions, in the absence and presence of organoclay. Epoxy systems were characterized by dynamic mechanical analysis (DMA), optical microscopy and X-ray diffraction. According to the obtained results, the cured DETA and DDS epoxy systems at elevated temperatures, above 180°C, showed a higher glass transition temperature (Tg) and thermal stability values than the system cured at low temperature (TETA). In addition, when the post-cure treatment was used, an improvement of the thermal stability was verified. When 1 phr (parts hundred resin) of organoclay was incorporated in DETA and DDS cured epoxy systems and post-cured, either the increase in the Tg and thermal stability values were more significant, especially for the system cured with DDS. Hence, the epoxy/DDS/organoclay system (exfoliated nanocomposite) is the most appropriate to be used as the matrix in the preparation of active composites since this matrix is thermally stable in the Ni-Ti shape memory alloy working range whose phase transformation occurs between 70 and 80 °C.

scholarly journals Precipitation Behavior of Thermo-Mechanically Treated Ti50Ni20Au20Cu10 High-Temperature Shape-Memory Alloy

2015 ◽  
Vol 2 (1) ◽  
pp. 29-36 ◽  
Author(s):  
Saif Haider Kayani ◽  
M. Imran Khan ◽  
Fazal Ahmad Khalid ◽  
Hee Young Kim ◽  
Shuichi Miyazaki
Keyword(s):  
High Temperature ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Precipitation Behavior

Transformation squence in a Cu-Al-Ni shape memory alloy at elevated temperatures

1986 ◽  
Vol 17 (1) ◽  
pp. 65-72 ◽  
Author(s):  
Jogender Singh ◽  
Haydn Chen ◽  
C. M. Wayman
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Elevated Temperatures

Finite Element Vibration Analysis of Composite Plates With Embedded Shape Memory Alloy Fibers at Elevated Temperatures

1995 ◽  
Author(s):  
Z. W. Zhong ◽  
Chuh Mei
Keyword(s):  
Finite Element ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Elevated Temperatures ◽  
Composite Plates ◽  
Nonlinear Material ◽  
Fiber Reinforced ◽  
Fiber Reinforced Composite ◽  
Reinforced Composite ◽  
Thermal Postbuckling

Abstract The present paper investigates the vibration behavior of the thermally buckled shape memory alloy (SMA) fiber-reinforced composite plates. The stress-strain relations are developed for a thin composite lamina with embedded SMA fibers. The finite element equation of motion including shape memory effect is presented. This equation can be mathematically separated into a static equation and a dynamic equation. The thermal postbuckling deflection and vibration of the thermally buckled position for SMA fiber-reinforced composite plates are determined. Due to the effects of nonlinear material properties of SMA, the vibration characteristics of thermally buckled composite plate with embedded SMA fibers are distinctly different from the one without SMA. Thermal postbuckling, natural frequencies and vibration modes for SMA reinforced composite rectangular plates are presented. Triangular plates with simply supported and clamped boundary conditions are also studied.

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