Compression, Bend, and Tension Studies on Forged Al67Ti25Cr8 and Al66Ti25Mn9 L12 Compounds

1990 ◽  
Vol 213 ◽  
Author(s):  
K.S. Kumar ◽  
S. A. Brown ◽  
J.D. Whittenberger
Keyword(s):  
Elevated Temperatures ◽  
Gradual Transition ◽  
Strain Gages ◽  
Strain Measurements ◽  
Transgranular Cleavage ◽  
Point Bend ◽  
Temperature Scanning ◽  
Increasing Temperature ◽  
Strength And Ductility ◽  
Scanning Electron

ABSTRACTCast, homogenized, and isothermally forged aluminum-rich L12 compounds Al87Ti25Cr8 and Al66Ti25Mn9 were tested in compression as a function of temperature and as a function of strain rate at elevated temperatures (1000K and 1100K). Three-point bend specimens were tested as a function of temperature in the range 300K to 873K. Strain gages glued on the tensile side of the ambient and 473K specimens enabled direct strain measurements. A number of “buttonhead” tensile specimens were electro-discharge machined, fine polished, and tested between ambient and 1073K for yield strength and ductility as a function of temperature. Scanning electron microscope (SEM) examination of fracture surfaces from both the bend and tensile specimens revealed a gradual transition from transgranular cleavage to intergranular failure with increasing temperature.

Temperature Dependence of Fracture Toughness of the Cubic (L12) Titanium Trialuminides

1996 ◽  
Vol 460 ◽  
Author(s):  
R. A. Varin ◽  
L. Zbroniec
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Room Temperature ◽  
Maximum Load ◽  
Gradual Transition ◽  
Transgranular Cleavage ◽  
Temperature Range ◽  
Temperature Fracture ◽  
Increasing Temperature ◽  
Work Of Fracture

ABSTRACTFracture toughness vs. temperature of the cubic (L12), Mn- modified titanium trialuminide (based on Al3Ti) was investigated in air at the temperature range up to 1000°C. Toughness calculated from the maximum load exhibits a broad peak (KQ≈7–10 MPara0,5) at the 200- 500°C temperature range and then decreases with increasing temperature, reaching a room temperature value of ∼4.5 MPam0.5 at 1000°C. However, the work of fracture (γWOF, J/m2) and the stress intensity factor calculated from it (KIWOF) increases continuously with increasing temperature. Fracture modes exhibit a gradual transition from transgranular cleavage at room temperature to predominantly intergranular failure at the 800- 1000°C range.

The Mechanical Properties of Fe-36.5Al and its Cr or ti Containing Alloys at Elevated Temperature

1994 ◽  
Vol 364 ◽  
Author(s):  
Dingqiang Li ◽  
Yi Liu ◽  
Aidang Shan ◽  
Dongliang Lin
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Ternary Alloys ◽  
Transgranular Cleavage ◽  
Feal Alloy ◽  
Fracture Surfaces ◽  
Increasing Temperature

AbstractThe mechanical properties of B2 structural FeAl alloys, prepared by hot rolling, at elevated temperatures have been measured by tensile tests. The alloys of Fe-36.5at.%A1, Fe-36.5at.%A1-5at.%Cr and Fe-36.5at.%Al-2at.%Ti were taken for tensile tests at a temperature range from room temperature to 1000°C. The fracture surfaces of these alloys were observed by SEM. The results showed that elongations of these alloys increased with increasing temperature when the testing temperatures were above 600°C. All the maximum elongations of these alloys appeared at 1000°C and those of Fe-36.5A1, Fe-36.5Al-5Cr, and Fe-36.5Al-2Ti alloys were 120%, 183% and 208% respectively. Fracture surfaces showed that failure of these alloys was by a combination of intergranular fracture and transgranular cleavage below 700°C. but showed a ductile fracture above 700°C. The ductility and strength of ternary alloys were higher than that of binary FeAl alloy at elevated temperatures, especially at high temperature. The <111> dislocations and helices have been observed in Fe-36.5A1 alloy by TEM. The large elongation of FeAl alloy at high temperature resulted from <111> dislocations slipping and <111> helices climbing.

Intracellular structures of rapid frozen biological samples observed by high-resolution low-temperature Scanning Electron Microscopy

1989 ◽  
Vol 47 ◽  
pp. 736-737
Author(s):  
T. Inoué ◽  
H. Koike
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Temperature ◽  
Liquid Nitrogen ◽  
Specimen Preparation ◽  
Chemical Fixation ◽  
Brown Adipose ◽  
Critical Point Drying ◽  
Temperature Scanning ◽  
Scanning Electron

Low temperature scanning electron microscopy (LTSEM) is useful to avoid artifacts such as deformation and extraction, because specimens are not subjected to chemical fixation, dehydration and critical-point drying. Since Echlin et al developed a LTSEM, many techniques and instruments have been reported for observing frozen materials. However, intracellular structures such as mitochondria and endoplasmic reticulum have been unobservable by the method because of the low resolving power and inadequate specimen preparation methods. Recently, we developed a low temperature SEM that attained high resolutions. In this study, we introduce highly magnified images obtained by the newly developed LTSEM, especially intracellular structures which have been rapidly frozen without chemical fixation.[Specimen preparations] Mouse pancreas and brown adipose tissues (BAT) were used as materials. After the tissues were removed and cut into small pieces, the specimen was placed on a cryo-tip and rapidly frozen in liquid propane using a rapid freezing apparatus (Eiko Engineering Co. Ltd., Japan). After the tips were mounted on the specimen stage of a precooled cryo-holder, the surface of the specimen was manually fractured by a razor blade in liquid nitrogen. The cryo-holder was then inserted into the specimen chamber of the SEM (ISI DS-130), and specimens were observed at the accelerating voltages of 5-8 kV. At first the surface was slightly covered with frost, but intracellular structures were gradually revealed as the frost began to sublimate. Gold was then coated on the specimen surface while tilting the holder at 45-90°. The holder was connected to a liquid nitrogen reservoir by means of a copper braid to maintain low temperature.

Criteria for the evaluation of low-temperature Scanning Electron Microscopy

1986 ◽  
Vol 44 ◽  
pp. 902-903
Author(s):  
Alan Beckett
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Temperature ◽  
Conformational Changes ◽  
Chemical Vapour ◽  
List Type ◽  
Dimensional Changes ◽  
Critical Point Drying ◽  
Temperature Scanning ◽  
Scanning Electron

Low temperature scanning electron microscopy (LTSEM) has been evaluated with special reference to its application to the study of morphology and development in microorganisms. A number of criteria have been considered and have proved valuable in assessing the standard of results achieved. To further aid our understanding of these results, it has been necessary to compare those obtained by LTSEM with those from more conventional preparatory procedures such as 1) chemical fixation, dehydration and critical point-drying; 2) freeze-drying with or without chemical vapour fixation before hand.The criteria used for assessing LTSEM for the above purposes are as follows: 1)Specimen immobilization and stabilization2)General preservation of external morphology3)General preservation of internal morphology4)Exposure to solvents5)Overall dimensional changes6)Cell surface texture7)Differential conformational changes8)Etching frozen-hydrated material9)Beam damage10)Specimen resolution11)Specimen life

Brittle fracture of nickel by dynamic indentation

1992 ◽  
Vol 7 (8) ◽  
pp. 1973-1975 ◽  
Author(s):  
J.W. Hoehn ◽  
T. Foecke ◽  
W.W. Gerberich
Keyword(s):  
Electron Microscopy ◽  
Brittle Fracture ◽  
Fracture Process ◽  
Low Energy ◽  
Face Centered Cubic ◽  
Dynamic Indentation ◽  
Transgranular Cleavage ◽  
Energy Process ◽  
Face Centered ◽  
Scanning Electron

Cracks of up to 40 μm which are either transgranular cleavage or very low energy “ductile” cracks have been introduced into large-grained fcc Ni. The mechanism for introducing this brittle fracture was dynamic indentation. Optical and scanning electron microscopy together with use of selected area channeling patterns were used to confirm that the fracture process is transgranular. The results qualitatively support the hypothesis that dynamic cracks originating in a brittle film can propagate relatively large distances into a ductile face-centered-cubic substrate by a rapid, low energy process.

scholarly journals Strengthening epoxy adhesives at elevated temperatures based on dynamic disulfide bonds

2020 ◽  
Vol 1 (9) ◽  
pp. 3182-3188
Author(s):  
Hsing-Ying Tsai ◽  
Yasuyuki Nakamura ◽  
Takehiro Fujita ◽  
Masanobu Naito
Keyword(s):  
Glass Transition ◽  
Disulfide Bonds ◽  
Epoxy Resins ◽  
Elevated Temperatures ◽  
Adhesive Properties ◽  
Epoxy Adhesives ◽  
Transition Points ◽  
Increasing Temperature

Epoxy resins incorporating aromatic disulfide bonds demonstrated improved adhesive properties with increasing temperature below their glass transition points.

Microstructure Evolution and Mechanical Properties of an Al-Cu-Mg Alloy at Elevated Temperature

2014 ◽  
Vol 1004-1005 ◽  
pp. 148-153
Author(s):  
Min Hao ◽  
Ji Gang Ru ◽  
Ming Liu ◽  
Kun Zhang ◽  
Liang Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Elevated Temperature ◽  
Elevated Temperatures ◽  
Shear Fracture ◽  
S Phase ◽  
Mg Alloy ◽  
Transmission Electron ◽  
Fracture Features ◽  
Scanning Electron

Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to study the microstructure and mechanical behavior of an Al-Cu-Mg alloy after tensile test at 125°C, 150°C, 175°C and 200 °C, respectively. The yield strength and ultimate tensile strength decreased with the increase of temperature, while the elongation increased firstly and then decreased. The S and S′ precipitate after tension at elevated temperatures. When the temperature was higher than 175°C, the precipitate coarsens rapidly. The alloys displayed a shear fracture features at elevated temperature. The larger S′ and S phase coarsened and dropped which forming crack in the grain boundaries and precipitate interfaces, resulting in the decrease of the elongation of the alloy.

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