scholarly journals Laboratory-Scale Processing and Performance Assessment of Ti–Ta High-Temperature Shape Memory Spring Actuators

2021 ◽  
Author(s):  
A. Paulsen ◽  
H. Dumlu ◽  
D. Piorunek ◽  
D. Langenkämper ◽  
J. Frenzel ◽  
...  
Keyword(s):  
High Temperature ◽  
Shape Memory ◽  
Detrimental Effect ◽  
Wire Drawing ◽  
Fast Heating ◽  
Heating And Cooling ◽  
Arc Melting ◽  
Ω Phase ◽  
And Performance

AbstractTi75Ta25 high-temperature shape memory alloys exhibit a number of features which make it difficult to use them as spring actuators. These include the high melting point of Ta (close to 3000 °C), the affinity of Ti to oxygen which leads to the formation of brittle α-case layers and the tendency to precipitate the ω-phase, which suppresses the martensitic transformation. The present work represents a case study which shows how one can overcome these issues and manufacture high quality Ti75Ta25 tensile spring actuators. The work focusses on processing (arc melting, arc welding, wire drawing, surface treatments and actuator spring geometry setting) and on cyclic actuator testing. It is shown how one can minimize the detrimental effect of ω-phase formation and ensure stable high-temperature actuation by fast heating and cooling and by intermediate rejuvenation anneals. The results are discussed on the basis of fundamental Ti–Ta metallurgy and in the light of Ni–Ti spring actuator performance.

Solid State Transformations and Equilibrium Crystal Structures of an Au-Cu Alloy with Shape Memory Effect

2012 ◽  
Vol 730-732 ◽  
pp. 859-864 ◽  
Author(s):  
Georgina Miranda ◽  
F.S. Silva ◽  
Delfim Soares
Keyword(s):  
High Temperature ◽  
Solid State ◽  
Shape Memory ◽  
Phase Transformations ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Equilibrium Phase ◽  
Lattice Parameters ◽  
Solid State Transformation ◽  
Heating And Cooling

Au-50%Cu (at. %) alloy presents the shape memory effect (SME), which is dependent of the solid state transformation that happens during heating, after the introduction of an internal stress in the quenched state. The solid state phase transformation temperatures were determined by means of Differential Thermal Analysis (DTA), both in heating and cooling cycles. With the obtained DTA results, a sequence of high temperature X-ray diffraction (XRD) experiments were made, in order to confirm the presence of the solid state phase transformations and to determine their stable crystal structure and lattice parameters. These XRD results were compared with those obtained from the literature. The displacements of the lattice parameters were determined, for each equilibrium phase, for measurements at room temperature and at high temperature. The characteristics of the quenched samples were also studied in order to determine the phase transformations that are responsible for the shape memory effect in this alloy.

scholarly journals Cyclic degradation of titanium–tantalum high-temperature shape memory alloys — the role of dislocation activity and chemical decomposition

2015 ◽  
Vol 08 (06) ◽  
pp. 1550062 ◽  
Author(s):  
T. Niendorf ◽  
P. Krooß ◽  
C. Somsen ◽  
R. Rynko ◽  
A. Paulsen ◽  
...  
Keyword(s):  
High Temperature ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Elevated Temperatures ◽  
Nickel Titanium ◽  
Chemical Decomposition ◽  
Ω Phase ◽  
The Matrix ◽  
Cyclic Degradation

Titanium–tantalum shape memory alloys (SMAs) are promising candidates for actuator applications at elevated temperatures. They may even succeed in substituting ternary nickel–titanium high temperature SMAs, which are either extremely expensive or difficult to form. However, titanium–tantalum alloys show rapid functional and structural degradation under cyclic thermo-mechanical loading. The current work reveals that degradation is not only governed by the evolution of the ω-phase. Dislocation processes and chemical decomposition of the matrix at grain boundaries also play a major role.

Microstructure and Phase Transformation Behavior of Ni-Mn-Fe High-Temperature Shape Memory Alloys

2015 ◽  
Vol 833 ◽  
pp. 63-66
Author(s):  
Cui Ping Wang ◽  
Yu Ding Liu ◽  
Shui Yuan Yang ◽  
Xing Jun Liu
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Transformation Behavior ◽  
Phase Transformation Behavior ◽  
Heating And Cooling ◽  
High Transformation ◽  
Irreversible Phase Transformation ◽  
Very High

The microstructure and phase transformation behavior of Ni-Mn-Fe high-temperature shape memory alloys including Ni40+xFe10Mn50-x (x = 0, 10) were investigated. The results show that both two alloys exhibit single fcc γ phase annealed at 900°C for 1 day. When these quenched alloys are again annealed at 500°C for 20 days, they almost exhibit main tetragonal θ martensite. The microstructural evolutions are consistent with the results of phase transformation measurements. It is clearly found that there is an irreversible phase transformation around 480°C ~ 570°C, which is associated with the formation of tetragonal θ martensite from γ phase. Afterwards, the reversible martensitic transformation occurs during heating and cooling with very high transformation temperature.

scholarly journals Breeding Vegetables Adapted to High Temperatures: A Case Study with Broccoli

HortScience ◽  
2011 ◽  
Vol 46 (8) ◽  
pp. 1093-1097 ◽  
Author(s):  
Mark W. Farnham ◽  
Thomas Bjorkman
Keyword(s):  
Abiotic Stress ◽  
High Temperature ◽  
Stress Tolerance ◽  
Abiotic Stress Tolerance ◽  
Vegetable Crop ◽  
Breeding Scheme ◽  
Selection Environment ◽  
And Performance ◽  
Improvement Effort

Breeding a vegetable crop for adaptation to a temperature regime that is higher than the recognized optimum for the species in question is an example of breeding for abiotic stress tolerance. Before embarking on a project to breed for such stress tolerance, we propose that several critical considerations or questions must be addressed. These considerations include the following: 1) What is the effect of the abiotic stress on the crop to be improved; 2) what will be the conditions of the selection environment; 3) what germplasm is available that contains the necessary genetic variation to initiate improvement; 4) what breeding scheme will be used to facilitate improvement; and 5) what will be the specific goals of the breeding effort? We use a case study with broccoli to breed for adaptation to high-temperature environments to provide examples of how each of these considerations might be addressed in developing an improvement effort. Based on documented success with this case study in which broccoli quality and performance under high-temperature summer environments has been improved, insights are provided that should be useful to future attempts to breed vegetables more tolerant of an abiotic stress.

Actuator from a Material with the High-Temperature Shape Memory Effect and Examples of its Application in Engineering

2016 ◽  
Vol 684 ◽  
pp. 523-529
Author(s):  
Vladimir Glushchenkov ◽  
Rinat Yu. Yusupov ◽  
Valentina Alekhina ◽  
Yuri Egorov
Keyword(s):  
High Temperature ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Experimental Technique ◽  
Shape Memory Material ◽  
Heating And Cooling ◽  
Memory Material ◽  
In Series

The report provides designs of actuators from the shape memory material-nitinol. It is proposed to use rods, wire, sheets and tape as working elements of the actuators. Special attention is paid to the designs of composite multil-element actuators, working elements of which are connected in parallel or in series. The experimental technique and results of experiments on evaluation of stresses developed by such actuators are given. It is shown that using the composite actuators from thin working elements facilitates control over their heating and cooling.

Fast Heating and Cooling for High Temperature Chemical Microreactors

2000 ◽  
pp. 514-525 ◽  
Author(s):  
Ch. Alépée ◽  
R. Maurer ◽  
L. Paratte ◽  
L. Vulpescu ◽  
Ph. Renaud ◽  
...  
Keyword(s):  
High Temperature ◽  
Fast Heating ◽  
Heating And Cooling

Study of as-cast Nb-Ru samples

MRS Advances ◽  
2018 ◽  
Vol 3 (34-35) ◽  
pp. 1949-1953
Author(s):  
S. Samal ◽  
L.A. Cornish
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Shape Memory ◽  
Optical Microscopy ◽  
Solid Solutions ◽  
Single Phase ◽  
Intermetallic Phases ◽  
Argon Atmosphere ◽  
Arc Melting ◽  
Cast Alloys

AbstractThe Nb-Ru system is of interest because the ∼NbRu phase has potential for high temperature shape memory alloys. Previous workers have identified the phase transformation variously as involving twinning, of cubic-to-tetragonal and tetragonal–to-orthorhombic (or monoclinic) transformations. As well as the terminal (Nb) and (Ru) solid solutions, two intermetallic phases have been identified: ∼NbRu and ∼NbRu3 / ∼Nb3Ru5 / ∼NbRu2, but the boundaries between the different phases are still not fully established. This investigation looked at six as-cast alloys of different compositions across the Nb-Ru system, which were made from 99.95 % purity Nb and Ru. The samples were made by arc-melting under an argon atmosphere, using titanium as an oxygen-getter. These samples were sectioned and prepared metallographically for optical microscopy, SEM and XRD analyses, the latter using an X’pert database. The phases found were (Nb), (Ru), ∼NbRu and “∼NbRu3”, as expected. Although the samples were mainly homogeneous, there was porosity in the (Ru) phase between the “∼NbRu3” dendrites in the Nb28.5:Ru71.5 at.% sample. The Nb14.2:Ru85.8 at.% sample was mainly single-phase (Ru).

Macroscopic modeling of NiTiHf under different loading modes: A finite difference method

2018 ◽  
Vol 29 (11) ◽  
pp. 2544-2553 ◽  
Author(s):  
Nazanin Farjam ◽  
Reza Mehrabi ◽  
Haluk Karaca ◽  
Mohammad Elahinia
Keyword(s):  
High Temperature ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Difference Method ◽  
Macroscopic Modeling ◽  
Heating And Cooling ◽  
Superelastic Behavior ◽  
Loading Modes

High-temperature shape memory alloys have remarkably solved the limitation of conventional shape memory alloys working at low levels of temperature and stress. The focus of this study is on a semi-analytical constitutive model for high-temperature shape memory alloys to predict their mechanical behavior. The model is based on Gibbs free energy, and the equations are simplified for NiTiHf at different loading conditions. A uniaxial compression case is used to validate the model with the experimental results. Superelastic behavior and also heating and cooling at different stress levels are compared to the experimental data reported in the literature. The nonlinear equations are solved using finite difference method, which is capable to calculate the distribution of strain and phase transformation along the cross section for various loading modes. Several more case studies on pure torsion and multiaxial loading are also investigated to show the capabilities of this approach.

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