Hot-hardness comparisons among isostructural Be12X intermetallic compounds

1993 ◽  
Vol 8 (7) ◽  
pp. 1550-1557 ◽  
Author(s):  
S.M. Bruemmer ◽  
B.W. Arey ◽  
J.L. Brimhall ◽  
J.P. Hirth
Keyword(s):  
Sharp Decrease ◽  
Slip Systems ◽  
Processing Conditions ◽  
Dislocation Mobility ◽  
Melting Temperatures ◽  
Brittle Transition ◽  
Metal Atoms ◽  
Macroscopic Plasticity ◽  
The Stability ◽  
Hot Hardness

Hot hardness has been measured in seven isostructural Be12X compounds: Be12Cr, Be12Mn, Be12V, Be12Mo, Be12Ti, Be12Ta, and Be12Nb. All vacuum-hot-pressed (VHP) materials exhibited similar hardness levels (800 to 1000 kg/mm2) at low temperatures (<600 °C), but sharply diverged at higher temperatures. Most compounds showed a sharp decrease in hardness above about one-half their melting temperatures except for Be12Nb and Be12Ti which maintained strength until higher temperatures. Ductile-brittle transition temperatures (DBTT's) of 600, 625, 690, 700, 700, and 850 °C were determined for Be12Cr, Be12Mn, Be12V, Be12Mo, Be12Ti, and Be12Nb, respectively. Hot-isostatically-pressed (HIP) and VHP Be12Nb heats both showed comparable behavior, indicating that the temperature required for macroscopic plasticity is not dependent on processing conditions. Differences in slip characteristics were observed between beryllides with similar melting temperatures, but differing DBTT's. Dislocations were activated on multiple slip systems in Bei2V during compressive deformation at 800 °C. Similar behavior was not observed in Be12Nb until test temperatures above 1000 °C. It is proposed that dislocation mobility may be related to the stability between Be12X and Be17X2 phases. Larger refractory metal atoms such as Nb may form faulted layers related to Be17X2 structures and thereby impede deformation at intermediate temperatures. Smaller atoms such as Cr, Mn, V, and Mo do not form a stable Be17X2 phase and thereby allow enhanced dislocation mobility at these temperatures.

scholarly journals Features of the damping capacity of Mn – Cu alloys

2021 ◽  
Vol 344 ◽  
pp. 01012
Author(s):  
Sergey Naumov ◽  
Svetlana Ginne
Keyword(s):  
Sharp Decrease ◽  
Alloying Elements ◽  
Damping Capacity ◽  
Natural Ageing ◽  
Cu Alloys ◽  
The Stability

Data on the damping capacity of Mn – Cu alloys are adduced. The results of studying the influence of alloying elements, natural ageing at temperatures of 293 K, 273 K and 263 K on the stability of the damping capacity of Mn – Cu alloys are presented. The high damping capacity of Mn – Cu alloys decreases by 4 ... 6 times during natural ageing at 293 K, remains during 1,7 years of natural ageing at 273 K and 263 K. The analysis of factors that should be considered responsible for a sharp decrease in the damping capacity of Mn – Cu alloys during natural ageing is submitted.

Tyramine Content of Raspberries and Other Fruit

1970 ◽  
Vol 53 (5) ◽  
pp. 1071-1073 ◽  
Author(s):  
D E Coffin
Keyword(s):  
Gas Chromatography ◽  
Processing Conditions ◽  
The Stability

Abstract The tyramine contents of 14 fruits and 9 fruit jams have been determined by gas chromatography of the trifluoroacetyl derivative of tyramine. Tyramine contents of more than 1 μg/g were found only in raspberries, raspberry jams, and 1 sample of apricot jam. The tyramine content of 15 samples of fresh raspberries varied from 12.8 to 92.5 μg/g; tyramine content of raspberry jams varied from 8.0 to 38.4 μ/g- The levels of tyramine in raspberries in relation to other fruit and the stability of tyramine under processing conditions indicate that it is a useful indicator of the presence of raspberry in fruit products. However, the wide variation in the levels of tyramine in raspberries indicates that it is not a satisfactory criterion for the estimation of the raspberry content of fruit products.

Electrically Conducting Compatible Blends Of Polyaniline / Poly (Vinyl Pyrrolidone)

1993 ◽  
Vol 328 ◽  
Author(s):  
William B. Stockton ◽  
M. F. Rubner
Keyword(s):  
Light Microscopy ◽  
Composition Range ◽  
Vinyl Pyrrolidone ◽  
Processing Conditions ◽  
Conductivity Measurements ◽  
Polar Solvents ◽  
Electrically Conducting ◽  
Solvent Cast ◽  
Poly Vinyl Pyrrolidone ◽  
The Stability

ABSTRACTBlending polyaniline (PAn) with a host polymer has the advantage of reducing the amount of polyaniline necessary for conductivity, increasing the stability of this conduction, and enhancing the overall mechanical integrity, versatility, and processability of PAn. PAn blends have generally been observed to be immiscible, reducing many of the above mentioned advantages. In this work, PAn was solution blended with poly (vinyl pyrrolidone) (PVP) in either NMP or DMAc, both polar solvents with an amide linkage. We have found PAn to be miscible with PVP under certain processing conditions. The extent of this compatibility and resulting mechanical properties were assessed by DMA, DSC, TGA, SAXS, and light Microscopy. DSC thermograms exhibit a single Tg for all blends ranging from 3 to 30 % by weight PAn. Light Microscopy and SAXS also suggest no phase separation. TGA results show that NMP binds very tightly to both PAn and PVP, with solvent cast blends retaining up to 20 wt% NMP, even after relatively vigorous drying. Electrical conductivity measurements of cast films show conductivity to range from 10-3to 2 S/cm over the same composition range.

Influence of Dislocation Mobility on Room and High Temperature Ductility of -Oriented Nial Single Crystals

1994 ◽  
Vol 364 ◽  
Author(s):  
M. A. Morris ◽  
J. P. Perez ◽  
R. Darolia
Keyword(s):  
High Temperature ◽  
Single Crystals ◽  
Room Temperature ◽  
Tensile Tests ◽  
Slip Systems ◽  
Dislocation Mobility ◽  
Screw Dislocations ◽  
Large Density ◽  
Thin Foils

AbstractThe dislocation configurations produced by room and high temperature compression of <100> oriented single crystals of binary NiAl and in those containing iron and hafnium additions have been analysed and compared to those obtained by hardness indentation and TEM insitu tensile tests. Kinking occurs during room temperature compression such that <100> dislocations are activated in all cases but the iron-containing alloy also exhibited a large density of <111> screw dislocations. The latter however, appear immobile when they are created by hardness indentations of thin foils, while only pile-ups of <100> segments can propagate. Similarly, although different slip systems are present after high temperature compression, only <100> dislocation segments have been confirmed to be mobile after room temperature hardness indentation of these predeformed thin foils. The improvement in ductility observed at room temperature in the predeformed specimens of the binary and the iron containing alloys has been attributed to the increased production of these mobile <100> dislocations.

Interfacial properties of all-polypropylene composites

e-Polymers ◽  
2010 ◽  
Vol 10 (1) ◽  
Author(s):  
Shadi Houshyar ◽  
Robert A. Shanks
Keyword(s):  
Optical Microscope ◽  
Processing Conditions ◽  
Polypropylene Composites ◽  
Melting Temperatures ◽  
Pull Out ◽  
Physico Chemical ◽  
Microbond Test ◽  
The Matrix ◽  
The Difference ◽  
Poly Propylene

AbstractPreparation and characterization of novel composites, consisting of polypropylene (PP) fibres in a random poly(propylene-co-ethylene) (PPE) matrix, were investigated. These composites possess unique properties, due to chemical compatibility of the two polymers allowing creation of strong physico-chemical interactions and strong interfacial bonds. The difference between the melting temperatures of PP fibre and PPE was exploited in order to establish processing conditions for the composites. Suitable conditions were chosen so that the matrix was a liquid, to ensure good wetting and impregnation of the fibres, though the temperature must not be high enough to melt the fibres. The morphology of the composites was investigated using optical and scanning electron microscopy. Optical microscope images showed that transcrystallization of the matrix was observed on PP fibre surfaces. SEM photographs displayed a thin layer of matrix on the reinforcement, attributed to good impregnation and wetting of the fibres. Adhesion between PPE matrix and PP fibres was characterized using a microbond test inspired by a fibre pull-out technique. The results showed that adhesion was appreciably increased when PP fibres were used instead of glass fibres in the matrix. Nevertheless, thermal processing conditions of the composites caused reduction in mechanical behaviour of the reinforcement.

Local cluster networks and the number of valence states in aluminium–transition metal face-centred icosahedral quasicrystals

2017 ◽  
Vol 232 (7-9) ◽  
Author(s):  
Koichi Kitahara ◽  
Kaoru Kimura
Keyword(s):  
Transition Metal ◽  
Local Cluster ◽  
Atom Ratio ◽  
Metal Atoms ◽  
Cluster Networks ◽  
Valence States ◽  
Transition Metal Atoms ◽  
Icosahedral Quasicrystals ◽  
The Stability ◽  
Good Agreement

AbstractCoordination environments of a special class of clusters which are related to the valence states in aluminium–transition metal face-centred icosahedral quasicrystals were analysed on the basis of the six-dimensional model of Katz and Gratias for the atomic sites and that of Yamamoto for the centres of the clusters. The number of the clusters per atom in the model (≈0.263) is comparable with that of Al–Cu–Ir cubic approximant crystal (≈0.258), and it indicates that the model reasonably represents the distribution of the clusters. We identified all the possible local cluster networks of short distances, which are related to the inter-cluster bonds, and evaluated the number of the valence states by assuming two possible configurations of inter-cluster bonds. The number of the valence states per atom was derived as a function of the fraction of transition-metal atoms, and the value is in good agreement with that expected from the compositions of real quasicrystals. Notably, the number of the part of the valence states which do not depend on the fraction of transition-metal atoms is numerically similar to the electron to atom ratio known as e/a, which is phenomenologically related to the stability of quasicrystals.

Plastic Deformation of Ti3Al and Ti3Al/TiA1 Polycrystals

1988 ◽  
Vol 133 ◽  
Author(s):  
S. A. Court ◽  
J. P. A. Löfvander ◽  
M. A. Stucke ◽  
P. Kurath ◽  
H. L. Fraser
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Covalent Bonding ◽  
Relative Activity ◽  
Slip Systems ◽  
Dislocation Mobility ◽  
Two Phase ◽  
Influence Of Temperature ◽  
Transmission Electron

ABSTRACTSamples of polycrystalline Ti3Al-base alloys, and a two phase Ti3Al/TiAl mixture have been deformed at room temperature and at elevated temperatures and examined subsequently by transmission electron microscopy in order to determine the influence of temperature and alloy content on the relative activity of the various slip systems. In particular, the detailed influence of covalent bonding on dislocation mobility in Ti3Al has been identified.

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