The Effect of Cyclic Transformation on the Shape Memory Characteristic in an Fe-Mn-Si-Cr-Ni alloy

1991 ◽  
Vol 246 ◽  
Author(s):  
Hideyuki Ohtsuka ◽  
S. Kajiwara ◽  
T. Ishihara
Keyword(s):  
Shape Memory ◽  
Nuclear Power ◽  
Optical Microscope ◽  
Reverse Transformation ◽  
Recovery Stress ◽  
Transmission Electron ◽  
Nucleation Sites ◽  
Ε Martensite ◽  
Memory Characteristic ◽  
Memory Characteristics

AbstractEvaluation of the shape memory characteristics under thermal and stress cycles is indispensable to ensure the reliability of shape memory alloys used in nuclear power reactors. Then the effect of γ↔E cyclic transformation on the shape memory characteristics was investigated in Fe-14Mn-6Si-9Cr-5Ni (wt%) alloy. ε martensites were stress-induced by pulling specimens at room temperature, and they were reverse transformed by heating under various stresses. The change of surface relief during reverse transformation was observed by a hightemperature optical microscope equipped with a tensile machine. The recovery stress was measured by this apparatus after the “yclic transformation” was repeated various times. The reverse-transformed microstructures were observed by transmission electron microscopy. As a result, the amount of residual ε martensite increased with increasing stress applied during reverse transformation. As the “cyclic transformation” was repeated, the recovery stress remarkably increased at first, and then gradually decreased. This rapid increase of recovery stress is attributed to not only the increase of elongation when specimen is deformed but also the increase of stacking faults which act as nucleation sites of martensite. The decrease of recovery stress is attributed to the decrease of elongation.

Effect of Buffer or Barrier Layer on Bistability for Nonvolatile Memory Fabricated with Al Nanocrystals Embedded in α-NPD

2006 ◽  
Vol 965 ◽  
Author(s):  
Sung-ho Seo ◽  
Woo-sik Nam ◽  
Jae-seok Kim ◽  
Chang-hyup Shin ◽  
Se-yun Lim ◽  
...  
Keyword(s):  
Barrier Layer ◽  
Nonvolatile Memory ◽  
Device Structure ◽  
Transmission Electron ◽  
Non Volatile Memory ◽  
Memory Characteristic ◽  
Layer Behavior ◽  
Volatile Memory ◽  
20 Nm ◽  
Memory Characteristics

ABSTRACTRecently, low molecular organic non-volatile memories have been developed as a next generation of non-volatile memory because of nano-meter device-feature size and nano-second access and store-time. We developed a non-volatile memory fabricated with the device structure of Al/ α-NPD/Al nano-crystals surrounded by Al2O3/α-NPD/Al, where α-NPD is N,N'-bis(1-naphthyl)-1,1'biphenyl4-4”diamine. One layer of Al nano-crystals with ∼20 nm-width ∼20 nm length was uniform produced between α-NPD layers, confirmed by 1.2MV high voltage transmission-electron-microscope. This device showed Vth of 3.0 V, Vprogram of 4.3 V, and Verase of 6.3 V. Particularly, this device exhibited an excellent non-volatile memory behavior performing the bi-stability (Iprogrm/Ierase) of >1×102, program/erase cycles of >1×105 and multi-levels. In addition, previous reports about low molecular organic non-volatile memories have showed a bad reproducible memory characteristic. However, this issue was completely solved via isolating Al nano-crystals embedded in α-NPD by O2 plasma oxidation. The uniformity of Vth, Vp, and Ve were 9.91%, 6.94% and 7.92%, respectively. Furthermore, the effect of buffer or barrier layer on non-volatile memory characteristics was investigate to examine the control ability for Vth, Vp, and Ve. The 0.5-nm LiF showed a barrier layer behavior suppressing the bi-stability of non-volatile memory. Otherwise, 15-nm CuPc exhibited a buffer layer behavior enhancing the bi-stability of nonvolatile memory.

scholarly journals Temperature-Induced Shape Memory Characteristics of Epoxy Resin-Based Fabric-Reinforced Composites

2013 ◽  
Vol 747 ◽  
pp. 785-787
Author(s):  
József Karger-Kocsis
Keyword(s):  
Carbon Fiber ◽  
Shape Memory ◽  
Epoxy Resin ◽  
Reinforced Composites ◽  
Recovery Stress ◽  
Dynamic Mechanical Analyzer ◽  
Carbon Fiber Fabric ◽  
Bending Mode ◽  
Fiber Fabric ◽  
Memory Characteristics

Shape memory characteristics of woven glass and carbon fiber fabric reinforced epoxy resin-based composites were assessed in bending mode using a dynamic mechanical analyzer. The reinforcement strongly improved the recovery stress but impaired the bending deformability. Composites with asymmetric fabric lay-up showed better performance when the reinforced section experienced local tension than compression during flexural loading.

scholarly journals Comparison of Reverse Transformation Behaviors of Thermally- and Deformation-Induced ε-Martensite in Fe-28Mn-6Si-5Cr Shape Memory Alloy

2016 ◽  
Vol 57 (10) ◽  
pp. 1707-1713 ◽  
Author(s):  
Wataru Tasaki ◽  
Koichi Tsuchiya ◽  
Takahiro Sawaguchi ◽  
Susumu Takamori
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Reverse Transformation ◽  
Ε Martensite

Study on the Two-Way Shape Memory Characteristics Induced by Compressive Loading Cycles

2010 ◽  
Vol 123-125 ◽  
pp. 1023-1026
Author(s):  
Young Ik Yoo ◽  
Jung Ju Lee
Keyword(s):  
Shape Memory ◽  
Niti Alloy ◽  
Compressive Loading ◽  
Memory Process ◽  
Recovery Stress ◽  
Maximum Deformation ◽  
Repetitive Loading ◽  
The One ◽  
Tubular Specimens ◽  
Memory Characteristics

The NiTi alloy can be trained by repetitive loading or heating cycles. As a result of the training, a two-way shape memory effect (TWSME) can be induced. Considerable research has been reported regarding the TWSME trained by tensile loading, however the TWSME trained by compressive loading has not been investigated nearly as much. In this research, six types of specimens (one solid cylindrical and five tubular) were used to obtain the two-way shape memory strain and two-way recovery stress and to evaluate the actuating capacity. The two-way actuating strain showed a saturated tendency after several training cycles for the same maximum deformation. A maximum value of the two-way strain was obtained for 7% of maximum deformation, independently of the geometry of the tubular specimens. The two-way strains obtained by the shape memory cycles and two-way recovery stress linearly increase as a function of the maximum deformation and the two-way strain, respectively, and the geometry of specimen affects the two-way recovery stress. Although the results show that sufficient recovery stress can be generated by either the two-way shape memory process or by the one-way shape memory process, the two-way shape memory process can be applied more conveniently to actuating applications.

Some early history of replica techniques for electron microscopy

1992 ◽  
Vol 50 (2) ◽  
pp. 1076-1077
Author(s):  
Robert M. Fisher
Keyword(s):  
Thin Film ◽  
Electron Microscopy ◽  
Optical Microscope ◽  
Early History ◽  
Bulk Materials ◽  
Thin Sections ◽  
Transmission Electron ◽  
Reflected Light ◽  
History Of ◽  
Electron Microscopes

By 1940, a half dozen or so commercial or home-built transmission electron microscopes were in use for studies of the ultrastructure of matter. These operated at 30-60 kV and most pioneering microscopists were preoccupied with their search for electron transparent substrates to support dispersions of particulates or bacteria for TEM examination and did not contemplate studies of bulk materials. Metallurgist H. Mahl and other physical scientists, accustomed to examining etched, deformed or machined specimens by reflected light in the optical microscope, were also highly motivated to capitalize on the superior resolution of the electron microscope. Mahl originated several methods of preparing thin oxide or lacquer impressions of surfaces that were transparent in his 50 kV TEM. The utility of replication was recognized immediately and many variations on the theme, including two-step negative-positive replicas, soon appeared. Intense development of replica techniques slowed after 1955 but important advances still occur. The availability of 100 kV instruments, advent of thin film methods for metals and ceramics and microtoming of thin sections for biological specimens largely eliminated any need to resort to replicas.

In situ observations of electromigration induced void behavior

1995 ◽  
Vol 53 ◽  
pp. 244-245
Author(s):  
T. Marieb ◽  
J. C. Bravman ◽  
P. Flinn ◽  
D. Gardner ◽  
M. Madden
Keyword(s):  
Electron Microscopy ◽  
Void Nucleation ◽  
Plan View ◽  
Transmission Electron ◽  
Nucleation Sites ◽  
Microelectronics Industry ◽  
In Situ Observations ◽  
Backscatter Electron Detector ◽  
Voltage Scanning

Electromigration and stress voiding have been active areas of research in the microelectronics industry for many years. While accelerated testing of these phenomena has been performed for the last 25 years[1-2], only recently has the introduction of high voltage scanning electron microscopy (HVSEM) made possible in situ testing of realistic, passivated, full thickness samples at high resolution.With a combination of in situ HVSEM and post-testing transmission electron microscopy (TEM) , electromigration void nucleation sites in both normal polycrystalline and near-bamboo pure Al were investigated. The effect of the microstructure of the lines on the void motion was also studied.The HVSEM used was a slightly modified JEOL 1200 EX II scanning TEM with a backscatter electron detector placed above the sample[3]. To observe electromigration in situ the sample was heated and the line had current supplied to it to accelerate the voiding process. After testing lines were prepared for TEM by employing the plan-view wedge technique [6].

Micro and Macromechanical Study of Stress-Induced Martensitic Transformation in a Cu-Al-Be Polycrystalline Shape Memory Alloy

2006 ◽  
Vol 509 ◽  
pp. 87-92 ◽  
Author(s):  
F.M. Sánchez ◽  
G. Pulos
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Vector Fields ◽  
Displacement Vector ◽  
Optical Microscope ◽  
Image Sequences ◽  
Tension Test ◽  
Loading Device ◽  
Stress States

An experimental investigation of the micro and macromechanical stress-induced martensitic transformation in a Cu-Al-Be polycrystalline shape memory alloy is undertaken using a uniaxial tension test. Digital images are acquired at different stress states. The image sequences are analyzed to estimate the optical flow to get displacement vector fields. The experiments are carried out on a miniature hydraulic loading device mounted under an optical microscope. The stress-strain curves and associated images show stress-induced martensitic transformation in specific grains. Displacement vector fields for the polycrystalline shape memory alloy are obtained. They are inhomogeneous due to the martensitic transformation and inter-granular interactions.

The Effect of Grain Size on Superplastic Deformation of Ti-6Al-4V Alloy

2007 ◽  
Vol 551-552 ◽  
pp. 387-392 ◽  
Author(s):  
Wen Juan Zhao ◽  
Hua Ding ◽  
D. Song ◽  
F.R. Cao ◽  
Hong Liang Hou
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Superplastic Deformation ◽  
Initial Strain Rate ◽  
Deformation Mode ◽  
Tensile Tests ◽  
Optical Microscope ◽  
Coarse Grained ◽  
Transmission Electron ◽  
Grain Growth Model

In this study, superplastic tensile tests were carried out for Ti-6Al-4V alloy using different initial grain sizes (2.6 μm, 6.5μm and 16.2 μm) at a temperature of 920°C with an initial strain rate of 1×10-3 s-1. To get an insight into the effect of grain size on the superplastic deformation mechanisms, the microstructures of deformed alloy were investigated by using an optical microscope and transmission electron microscope (TEM). The results indicate that there is dramatic difference in the superplastic deformation mode of fine and coarse grained Ti-6Al-4V alloy. Meanwhile, grain growth induced by superplastic deformation has also been clearly observed during deformation process, and the grain growth model including the static and strain induced part during superplastic deformation was utilized to analyze the data of Ti-6Al-4V alloy.

Organoclay-reinforced polyethersulfone-modified epoxy-based hybrid nanocomposites

2011 ◽  
Vol 23 (7) ◽  
pp. 526-534 ◽  
Author(s):  
Yang Wang ◽  
Boming Zhang ◽  
Jinrui Ye
Keyword(s):  
Electron Microscopy ◽  
Fracture Toughness ◽  
Electron Microscope ◽  
Optical Microscope ◽  
Mechanical Analysis ◽  
Hybrid Nanocomposites ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Modified Epoxy ◽  
Scanning Electron

Hybrid nanocomposites were successfully prepared by the incorporation of polyethersulfone (PES) and organoclay into epoxy resin. They had higher fracture toughness than the prepared PES/epoxy blend and organoclay/epoxy nanocomposites. The microstructures of the hybrid nanocomposites were studied. They were comprised of homogeneous PES/epoxy semi-interpenetrating network (semi-IPN) matrices and organoclay micro-agglomerates made up of tactoid-like regions composed of ordered exfoliated organoclay with various orientations. The former was confirmed with dynamic mechanical analysis, scanning electron microscopy and transmission electron microscopy, while the latter was successfully observed with X-ray diffraction measurements, optical microscope, scanning electron microscope and transmission electron microscope. The improvement of their fracture toughness was due to the synergistic toughening effect of the PES and the organoclay and related to their microstructures.

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