Cooling and Heating Characteristics of Ti-Ni Based Shape Memory Alloy Wire Actuators

2007 ◽  
Vol 124-126 ◽  
pp. 1649-1652 ◽  
Author(s):  
Jung Min Nam ◽  
Jae Hwa Lee ◽  
Yun Jung Lee ◽  
Tae Hyun Nam
Keyword(s):  
Cooling Rate ◽  
Heating Rate ◽  
Vacuum Induction Melting ◽  
Induction Melting ◽  
Heating Rates ◽  
Cooling Rates ◽  
Alloy Wire ◽  
Heating And Cooling ◽  
High Heating ◽  
Better Than

Ti-51Ni(at%) and Ti-40Ni-10Cu(at%) alloy wires with diameters of 0.3mm, 0.5mm and 0.7mm were prepared by drawing the alloy ingots fabricated by vacuum induction melting. Heating rates of the wires were investigated by measuring changes in temperatures of them while applying currents in the range of 1 A and 6 A to them and cooling rates were investigated by measuring changes in temperatures of them after cutting currents. Heating rate increased with increasing the amount of current, while cooling rate was kept constant. Both heating rate and cooling rate increased with decreasing diameter of wire. This suggested that high amount of current and small wire diameter were required for high heating and cooling rate. Comparing Ti-50Ni alloy wires with Ti-40Ni-10Cu alloy wires, heating rates of the latter was faster than that of the former, although cooling rates were almost same. This suggested that Ti-40Ni-10Cu alloy wires is better than Ti-50Ni alloy wires for the applications requiring high actuating rates.

scholarly journals Thermal stress, cooling-rate and fictive temperature of silicate melts

2021 ◽  
Vol 176 (10) ◽  
Author(s):  
Sharon L. Webb
Keyword(s):  
Heat Capacity ◽  
Cooling Rate ◽  
Heating Rate ◽  
Calibration Curve ◽  
Silicate Melts ◽  
Internal Stresses ◽  
Heating Rates ◽  
Fictive Temperature ◽  
Slow Cooling ◽  
Cooling Rates

AbstractThe unknown cooling-rate history of natural silicate melts can be investigated using differential scanning heat capacity measurements together with the limiting fictive temperature analysis calculation. There are a range of processes occurring during cooling and re-heating of natural samples which influence the calculation of the limiting fictive temperature and, therefore, the calculated cooling-rate of the sample. These processes occur at the extremes of slow cooling and fast quenching. The annealing of a sample at a temperature below the glass transition temperature upon cooling results in the subsequent determination of cooling-rates which are up to orders of magnitude too low. In contrast, the internal stresses associated with the faster cooling of obsidian in air result in an added exothermic signal in the heat capacity trace which results in an overestimation of cooling-rate. To calculate cooling-rate of glass using the fictive temperature method, it is necessary to create a calibration curve determined using known cooling- and heating-rates. The calculated unknown cooling-rate of the sample is affected by the magnitude of mismatch between the original cooling-rate and the laboratory heating-rate when using the matched cooling-/heating-rate method to derive a fictive temperature/cooling-rate calibration curve. Cooling-rates slower than the laboratory heating-rate will be overestimated, while cooling-rates faster than the laboratory heating-rate are underestimated. Each of these sources of error in the calculation of cooling-rate of glass materials—annealing, stress release and matched cooling/heating-rate calibration—can affect the calculated cooling-rate by factor of 10 or more.

scholarly journals XPS and Electron Microscopy Study of Oxide-Scale Evolution on Ignition Resistant Mg-3Ca Alloy at Low and High Heating Rates

2020 ◽  
Vol 1 ◽  
Author(s):  
L. A. Villegas-Armenta ◽  
R. A. L. Drew ◽  
M. O. Pekguleryuz
Keyword(s):  
Oxide Scale ◽  
Heating Rate ◽  
Photoelectron Spectroscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
High Heating Rate ◽  
Heating Rates ◽  
Oxide Interface ◽  
Protective Oxide ◽  
High Heating

AbstractEarlier work by the authors suggested that the formation of molten eutectic regions in Mg-Ca binary alloys caused a discrepancy in ignition temperature when different heating rates are used. This effect was observed for alloys where Ca content is greater than 1 wt%. In this work, the effect of two heating rates (25 °C/min and 45 °C/min) on the ignition resistance of Mg-3Ca is evaluated in terms of oxide growth using X-ray Photoelectron Spectroscopy. It is found that the molten eutectic regions develop a thin oxide scale of ~100 nm rich in Ca at either heating rate. The results prove that under the high heating rate, solid intermetallics are oxidized forming CaO nodules at the metal/oxide interface that eventually contribute to the formation of a thick and non-protective oxide scale in the liquid state.

scholarly journals Effects of Heating Rate on Formation of Globular and Acicular Austenite during Reversion from Martensite

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 266 ◽  
Author(s):  
Xianguang Zhang ◽  
Goro Miyamoto ◽  
Yuki Toji ◽  
Tadashi Furuhara
Keyword(s):  
Heating Rate ◽  
High Temperatures ◽  
The Other ◽  
Growth Mode ◽  
High Heating Rate ◽  
Heating Rates ◽  
Other Hand ◽  
High Heating ◽  
Martensite Matrix

The effects of heating rate on the formation of acicular and globular austenite during reversion from martensite in Fe–2Mn–1.5Si–0.3C alloy have been investigated. It was found that a low heating rate enhanced the formation of acicular austenite, while a high heating rate favored the formation of globular austenite. The growth of acicular γ was accompanied by the partitioning of Mn and Si, while the growth of globular γ was partitionless. DICTRA simulation revealed that there was a transition in growth mode from partitioning to partitionless for the globular austenite with an increase in temperature at high heating rate. High heating rates promoted a reversion that occurred at high temperatures, which made the partitionless growth of globular austenite occur more easily. On the other hand, the severer Mn enrichment into austenite at low heating rate caused Mn depletion in the martensite matrix, which decelerated the reversion kinetics in the later stage and suppressed the formation of globular austenite.

Effect of Cooling Rate on the Microstructure of Cu80Cr20 Alloys

2011 ◽  
Vol 694 ◽  
pp. 704-707
Author(s):  
Z.M. Zhou ◽  
W.J. Huang ◽  
J. Luo ◽  
X.P. Li ◽  
T. Zhou ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cooling Rate ◽  
Electromagnetic Levitation ◽  
Vacuum Induction Melting ◽  
Induction Melting ◽  
Rich Phase ◽  
Arc Melting ◽  
Splat Quenching ◽  
Scanning Electron

The effect of cooling rate on the microstructure of Cu80Cr20 alloys was studied by using vacuum non-consumable arc melting, vacuum induction melting, electromagnetic levitation and splat quenching. The microstructure evolution of the Cr-rich were analyzed by scanning electron microscopy (SEM) and optical microscopy. The results showed that nonuniform Cr-rich dendrite distributes on Cu-rich matrix for arc melted alloys and uniform Cr-rich dendrite distributes on Cu-rich matrix for electromagnetic levitation melted alloys and vacuum induction melted alloys. However, the Cr-rich phase show both dendrites and spheroids for splat quenched alloys. This means liquid phase separation occurred during rapid solidification.

scholarly journals Microstructure Evolution of Selective Laser Melted Inconel 718: Influence of High Heating Rates

Metals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 587 ◽  
Author(s):  
Seyedmohammad Tabaie ◽  
Farhad Rézaï-Aria ◽  
Mohammad Jahazi
Keyword(s):  
Heating Rate ◽  
Inconel 718 ◽  
Microstructural Analysis ◽  
Secondary Phases ◽  
Heating Rates ◽  
Laser Melting ◽  
Microstructural Characteristics ◽  
High Heating ◽  
In718 Superalloy ◽  
Confocal And Electron Microscopy

Inconel 718 (IN718) superalloy samples fabricated by selective laser melting (SLM) were submitted to different heating cycles and their microstructural characteristics were investigated. The selected heating rates, ranging from 10 °C/min to 400 °C/s, represent different regions in the heat-affected zone (HAZ) of welded additively manufactured specimens. A combination of differential thermal analysis (DTA), high-resolution dilatometry, as well as laser confocal and electron microscopy were used to study the precipitation and dissolution of the secondary phases and microstructural features. For this purpose, the microstructure of the additively manufactured specimen was investigated from the bottom, in contact with the support, to the top surface. The results showed that the dissolution of γ″ and δ phases were delayed under high heating rates and shifted to higher temperatures. Microstructural analysis revealed that the Laves phase at the interdendritic regions was decomposed in specific zones near the surface of the samples. It was determined that the thickness and area fraction of these zones were inversely related to the applied heating rate. A possible mechanism based on the influence of heating rate on Nb diffusion in the interdendritic regions and core of the dendrites is proposed to interpret the observed changes in the microstructure.

scholarly journals Latent Heating and Cooling Rates in Developing and Nondeveloping Tropical Disturbances during TCS-08: Radar-Equivalent Retrievals from Mesoscale Numerical Models and ELDORA*

2013 ◽  
Vol 70 (1) ◽  
pp. 37-55 ◽  
Author(s):  
Myung-Sook Park ◽  
Andrew B. Penny ◽  
Russell L. Elsberry ◽  
Brian J. Billings ◽  
James D. Doyle
Keyword(s):  
Tropical Cyclone ◽  
Doppler Radar ◽  
Critical Role ◽  
Evaporative Cooling ◽  
Latent Heating ◽  
Heating Rates ◽  
Cooling Rates ◽  
Heating And Cooling ◽  
Cooling Effects ◽  
Convective Cells

Abstract Latent heating and cooling rates have a critical role in predicting tropical cyclone formation and intensification. In a prior study, Park and Elsberry estimated the latent heating and cooling rates from aircraft Doppler radar [Electra Doppler Radar (ELDORA)] observations for two developing and two nondeveloping tropical disturbances during the Tropical Cyclone Structure 2008 (TCS-08) field experiment. In this study, equivalent retrievals of heating rates from two mesoscale models with 1-km resolution are calculated with the same radar thermodynamic retrieval. Contoured frequency altitude diagrams and vertical profiles of the net latent heating rates from the model are compared with the ELDORA-retrieved rates in similar cloud-cluster regions relative to the center of circulation. In both the developing and nondeveloping cases, the radar-equivalent retrievals from the two models tend to overestimate heating for less frequently occurring, intense convective cells that contribute to positive vorticity generation and spinup in the lower troposphere. The model maximum cooling rates are consistently smaller in magnitude than the heating maxima for the nondeveloping cases as well as the developing cases. Whereas in the model the cooling rates are predominantly associated with melting processes, the effects of evaporative cooling are underestimated in convective downdraft regions and at upper levels. Because of the net warming of the columns, the models tend to overintensify the lower-tropospheric circulations if these intense convective cells are close to the circulation center. Improvements in the model physical process representations are required to realistically represent the evaporative cooling effects.

Porous TiNi Synthesis from Elemental Powders

1994 ◽  
Vol 360 ◽  
Author(s):  
Janet C. Hey ◽  
A. Peter Jardine
Keyword(s):  
Pure Metal ◽  
Vacuum Arc ◽  
Vacuum Induction Melting ◽  
Induction Melting ◽  
Heating Rates ◽  
Chemical Homogeneity ◽  
Vacuum Arc Remelting ◽  
Porous Microstructures ◽  
Cold Pressed ◽  
Alloy Tini

AbstractThe shape memory alloy TiNi is produced by either Vacuum Induction Melting (VIM) or by Vacuum Arc Remelting (VAR) of pure metal ingots for actuator applications. Powder metallurgy techniques provide an alternative fabrication route for their use in passive damping applications where porosity and deviations in chemical homogeneity can be tolerated. In this study TiNi compacts were cold pressed from the blended elemental powders and sintered in vacuum for varying times at temperatures from 800°C to 1000°C. Two heating rates were used, 5 K/min. and 10 K/min. A TiNi microstructure could be produced after annealing at 1000°C for 6 h., although some TiNi3 was still observed. Sintering above 900°C produced porous microstructures with green densities approaching 3.5 gm/cm3.

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