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1.
Anisotropy in the Knoop indentation hardness and the friction of diamond cones on calcium fluoride crystals has been investigated at experimental temperatures from 20 to 300° C. It is shown that the directions of minimum and maximum indentation hardness, on the (001) plane, are 110 and 100 respectively whilst the 1¯10 are harder than the 11¯2 directions on the (111) plane. Also, the sliding friction in the (001) plane is greatest in the 110 directions and least in the 100 and, on the (111) cleavage plane, [¯1¯12] sliding leads to higher friction than [11¯2]. The nature of anisotropy, for both hardness and friction measurements, does not change over the experimental temperature range covered in this work. Observations on the resultant deformation are made and these anisotropic properties are explained in terms of the effective resolved shear stresses developed on the {100} 011 primary slip systems at all experimental temperatures. 相似文献
2.
An imperfectly B2 ordered Fe3Al aggregate was cast, thermomechanically hot rolled and finally annealed at 870 K. Subsequently, the specimen was rolled at 800–830 K to a strain of 80%. The microstructure and the crystallographic texture of the rolled polycrystalline sample was investigated within the range =20–80%. The microstructure consisted of flat, elongated grains. In numerous grains straight slip lines were detected. Even after =80% recrystallization was not observed. The rolling texture of Fe3Al considerably deviates from that of non-ordered body centered cubic (b.c.c.) alloys and pure b.c.c. metals. The {111}uvw texture fibre (7-fibre) was very pronounced, while the {hkl}110 fibre (-fibre) was very weak. The {112}110 orientation which represents the strongest texture component in non-ordered b.c.c. alloys did not occur at all. The textures are discussed in terms of the {110}111, {112}111, {112}111 and {123}111 slip systems. The contribution of crystallographic slip of the various types of potential slip systems was simulated by means of the Taylor theory. 相似文献
3.
Tensile tests at 20° C have been carried out on seventy-three sapphire whiskers and on seventeen silicon nitride whiskers. The sapphire whiskers were of 0001, 1¯120, 10¯10, and 10¯11 orientations, while the silicon nitride whiskers were 0001, 11¯20, and 10¯13. Tensile strengths were in the range 45 to 1500 kg/mm2, and deformation was found to be purely elastic. The tensile strength data have been analysed and fitted to empirical equations describing the effect of size on strength for different orientations. These empirical equations have been used to deduce possible fracture nucleation mechanisms. It is concluded that, in the case of 0001 sapphire whiskers, fracture nucleation may be due to dislocation pile-ups or interactions, while in the other cases a Griffith flaw mechanism is probably applicable. 相似文献
4.
Recrystallization textures in rolled copper specimens have been investigated so as to elucidate the mechanisms of cube texture formation. The specimens are single crystals with the orientations corresponding to the main components of the rolled textures, such as {112}111,{110}112, etc. and bicrystals consisting of such oriented crystals. The cube texture was not observed in any single crystal specimens, but observed in only two bicrystal specimens with {112}/111{100}001 and {110}112/{100}001 orientations. The formation of cube texture seems to require the existence of a cube oriented region in the deformed state, and the favourable oriented matrix to allow the growth of such nuclei. 相似文献
5.
Polycrystalline Co-49.3at% Al which had been extruded at 1505 K was examined using transmission electron microscopy. Diffraction contrast analysis showed that b = 100 as well as b = 111 dislocations contribute to elevated temperature deformation in CoAl. Therefore, it was concluded that sufficient slip systems exist in CoAl to allow for general plasticity in the absence of diffusional mechanisms. Since no examples of b = 110 dislocations were found, the importance of 110{1¯10} slip in CoAl at 1505 K is unclear. Dislocations of the type b = 001 were observed on both {110} and {100} planes while b = 111 dislocations were observed on {1¯10} planes. 相似文献
6.
The growth of twinned crystals of aluminium on solidification is discussed with reference to the structure of the growing tip. It is shown that one must differentiate between two types of 112 growth directions in the twin boundary. Normally, all the tips grow in the same type of 112 growth direction and this particular type may give the tip a favourable shape, possibly by producing a sharp edge. If a tip is growing in a less favourable 112 direction, the favourable type can be established by the twins changing sides. This is observed to occur regularly in the continuous casting method according to Hunter. The re-entrant edge mechanism is not supported by the present results. 相似文献
7.
The ratios of the plastic shear strain and tensile strain to the resolved shear strain are determined on the basis of earlier results obtained by computer for 1 0 0 and 1 1 1 textures and nontextured polycrystals in the case of simultaneous shear and extension. It is shown that the plastic deformation increment vector determined by the application of the plastic work equation fulfils the normality condition prescribed by the generalized flow law. 相似文献
8.
The 100, 111 and 110 textures of copper electrodeposits obtained from copper sulfate baths changed to the 100, 100 and
textures, respectively, after recrystallization. The textures of chromium electrodeposits obtained from the standard Sargent bath remained unchanged after recrystallization. The results are in agreement with the prediction of the strain energy release maximization model, in which the recrystallized grains orient themselves so that their minimum elastic modulus direction can be parallel to the absolute maximum internal stress direction due to dislocations in the non-recrystallized grains. 相似文献
9.
The mechanism of continuous dissolution was studied using transmission electron microscopy, X-ray diffraction and hardness measurements. The metastable phase was identified in the first stage of dissolution nucleating at the - boundaries. Interface dislocations at the - boundaries forming a perpendicular net in the 110 directions were identified as of screw character and of Burgers vector b=1/2a 110. During dissolution a change of shape of precipitates occurs leading to their fragmentation and to a change of the direction of boundaries into 110 directions. 相似文献
10.
Photosensitive Centers in CdTe〈Ge〉, CdTe〈Sn〉, and CdTe〈Pb〉 总被引:1,自引:0,他引:1
P. N. Gorlei O. A. Parfenyuk M. I. Ilashchuk K. S. Ul'yanitskii V. R. Burachek S. N. Chupyra 《Inorganic Materials》2003,39(11):1127-1131
The spectral and temperature dependences of photoconductivity in CdTePb crystals under band-gap and combined excitation were studied at photon energies in the range 0.53–1.7 eV and temperatures from 80 to 300 K. The high photosensitivity of the crystals and the observed IR and temperature quenching of photoconductivity indicate that, just as in CdTeGe and CdTeSn, the recombination processes in CdTePb are dominated by deep centers with drastically different capture cross sections for electrons and holes. Some parameters of the centers are determined. The results suggest that the likely defect species responsible for the high photosensitivity of CdTePb is an acceptor complex consisting of a Cd vacancy and a metal (Ge, Sn, Pb) ion on the Cd site: (V
2–
CdM+)–/0. 相似文献
11.
CdS, CdSe, and CdTe single crystals were vapor-phase-doped with the corresponding silicon chalcogenides under nearly equilibrium conditions. Cathodoluminescence studies revealed that the Si dopant produced new luminescence centers in the crystals. The cathodoluminescence spectra of Cd4SiS6and Cd4SiSe6crystals were measured. Metastable, sphalerite CdSSi and CdSeSi films were grown under highly nonequilibrium conditions. The maximum of edge emission in their spectra was redshifted as compared to the stable materials. The CdSSi and CdSeSi crystals were shown to be photosensitive. 相似文献
12.
The texture of electrodeposited iron foil has been measured. It was observed that the deposited iron foil had a {110} uvw type texture. If a sufficiently strong magnetic field was applied along the deposited layer during the deposition process, a {110} 001 texture developed from the initial {110} uvw texture, with the 001 axis parallel to the direction of the applied field. An attempt has been made to explain the mechanism of texture development, as well as the effect of the magnetic field during the deposition process. 相似文献
13.
A crystallographic analysis of the atom positions in the unit cell of the R-phase of the TiNi shape memory alloy has been performed. In addition to a homogeneous shape change the atoms are found to shuffle in the [111]B2 and –211B2 directions during the B2 to R-phase transformation. The origin of these shuffles is found to be a complex interaction between 1101–10 transverse acoustic and 111 longitudinal acoustic soft phonon modes. 相似文献
14.
Y. G. Wang H. Q. Ye K. H. Kuo X. J. Feng G. L. Liao S. Z. Long 《Journal of Materials Science》1991,26(21):5725-5732
Samples having the nominal composition of Ca3SrAl6SO16 were sintered at 1380 °C and analysed by electron diffraction. The frequent appearances of forbidden and satellite reflections in this compound imply the presence of a number of basal and nonbasal superlattices so that the microstructure of this cement clinker was characterized by various superstructures including one-, two- and even three-dimensional superstructures along the 0 0 1, 1 1 0, 1 1 2, 1 1 4 or 2 2 1, 0 1 3 and 1 2 3 directions with repeat periods of two or three times of that of basic one, respectively, and intergrowth of these. Various domain structures with 90°, 120° and 48.2°, etc., orientation relationships were also detected in these superstructures and the total number of these orientation variants related to the symmetry elements lost in the process of phase transformation, can be predicted according to the conclusions of Van Tendeloo and Amerlinckx, or they are equal to the number of those unique planes in the matrix. 相似文献
15.
The textures of two different conical shaped liners, fabricated by the same forging processes from arc-cast and powder-sintered ingots, were investigated by using neutron-diffraction measurements and three-dimensional orientation-distribution-function (ODF) analysis. The major textures of both liners could be described by the (1 1 1) uv w and (1 0 0) u v w type. The two liners had essentially identical texture at the 8 cm position (measured from the base of the cone) with strong sheet-type texture components, i.e. (1 1 1) ¯1 0 1, (1 1 1) ¯1 1 0 and (1 0 0) 0 1 1. However, the dominant textures at the 3 cm positions were 1 1 1 and 1 0 0 fibre textures with the fibre axes oriented parallel to the normal direction in both liners. A strong cube texture was observed at the 3 cm position of the arc-cast liner but it was not observed for the powder-sintered liner. The arc-cast liner had a generally higher degree of texture than the powder-sintered liner. 相似文献
16.
The birefringence topography of a Bi12GeO20 single crystal which has a strong natural optical activity is presented. The natural optical activity of the crystal may be completely compensated by reflection polarised light microscopy so that the birefringence images of dislocations and subboundaries are observed. The Burgers' vectors of dislocations were found to be of the types 1/2 1 1 1, 1 0 0 and 1 1 0 and dislocations which form subboundaries are also of these types. 相似文献
17.
On the basis of computer-calculated yield functions, the work hardening of 100 textured Cu-0.64 at % Co-0.48 at % Si and 111 textured polycrystalline copper wires were studied by simultaneous torsion and extension and by pure extension. Representing the work hardening by resolved shear stress-resolved shear strain curves, the rate of hardening is significantly lower for torsion than for pure extension. This behaviour is explained by the operation of different slip systems activated in the two modes of deformation. In the 100 textured Cu-Co-Si wires, heterogeneous plastic deformation was observed beyond about 80% shear strain. 相似文献
18.
Chemical vapor deposition of polycrystalline diamond films is studied by combining an atomic-scale kinetic Monte Carlo model with two one three-dimensional and one two-dimensional grain-scale models. The atomic-scale model is used to determine the growth rates of 111- and 100-oriented surface facets, the surface morphology of the facets and the extent of incorporation of the crystal defects. Using the atomic-scale modeling predicted growth rates for the 111- and 100-oriented facets, grain-scale modelling is carried out to determine the evolution of grain structure, surface morphology and crystallographic texture in the polycrystalline diamond films. It is found that depending on the relative growth rates of the 111- and 100-oriented facets, which can be controlled by selecting the CVD processing conditions, one can obtain either 110-textured films with a relatively smooth faceted surface or 100-textured films with a highly pronounced deep facets. In both cases, however, the film surface is composed entirely of the 111 facets. This findings are found to be fully consistent with the available experimental results. 相似文献
19.
G. Torres-Villaseñor R. Barrio-Paredes S. Victor Radcliffe 《Journal of Materials Science》1978,13(10):2164-2170
The stress-strain behaviour under compresion at constant strain rate of single crystals (051 and 122) compression axis) and polycrystalline samples of cuprous oxide have been examined at room temperature and hydrostatic pressure up to 12 kb and at atmospheric pressure and high temperature up to 600° C. At high environmental pressure, plastic flow occurs at 6 kb. At high temperatures and one atmosphere, extensive plastic deformation was observed after 500° C. The resultant slip planes were of the {110} and {100} types. Transmission electron microscopy of thin foils prepared from deformed specimens shows that the Burgers' vectors of the glide dislocations are of the 111, 110 and 100 types. 相似文献
20.
The isothermal transformation behaviour of the metallic glass Fe40Ni40P14B6 between 320 and 400° C is described. Crystallization occurs by a eutectic mechanism to form Fe-Ni austenite and a body-centred tetragonal phase which is isomorphous with Fe3P and Ni3P. The eutectic crystals have a barrel shape such that the c-axis of the tetragonal phase is parallel to the barrel axis. The orientation relationship between the two phases is 1 1 0T 1 1 0 and 0 0 1T 1 1 2. The austenite phase contains (1 1 1) twins. 相似文献