A single crystal of HgTe was grown by the Bridgman method and annealed in Hg or Te vapour. The Hall coefficient and the electrical conductivity were measured on the annealed crystals in the temperature range between 77 K and room temperature. The electrical conductivity increased with annealing partial pressure. The p-n turning temperature of the sign of the Hall coefficient. RH of Hg-annealed crystal fell with increasing Hg partial pressure, while that of Te-annealed crystal rose. The carrier concentration was calculated from the Hall coefficient RH in the temperature range of exhausion near 77 K by a single carrier model. The Hg partial pressure of p-n transition was obtained from the dependence of carrier concentration upon the Hg partial pressure. The i-boundary corresponding p-n transition and lines of equivalent carrier concentration were drawn on the P-T phase diagram for the Hg-Te system.
The permeation response of hydrogen and deuterium through α-iron in the oscillating pressure condition was measured to determine the diffusion coefficient without influence of surface effects. The diffusion coefficients of hydrogen and deuterium in α-iron at temperatures from 500 to 1000 K are: (This article is not displayable. Please see full text pdf.) The ratio of the diffusion coefficients of hydrogen isotopes (DH⁄DD) depends on the temperature; the value of the ratio approaches to unity with increasing temperature. This behavior differs from that of fcc metals in which the value of the ratio approaches to \sqrt2 with increasing temperature. The isotope effect of hydrogen diffusivity in α-iron can not be explained by the classical rate theory, and the quantum-mechanical correction for it is needed.
The effect of cold rolling on the fatigue life and the structural change of Ni75Si8B17 and Co75Si10B15 ribbon amorphous alloys during cyclic stressing was investigated by a pulsating tension fatigue test, X-ray diffraction and high resolution transmission electron microscopy. In a micro-Vickers hardness test, both alloys became softer after cold rolling. In the case of the fatigue, a considerably different behavior was shown between as-quenched and rolled specimens. Futhermore, by means of the pair distribution function method and the observation by transmission electron microscopy, it was confirmed that in the amorphous alloys the microscopic structural change was induced by the cold rolling and the excessively accumulated damage due to a number of stress cycles.
The superplasticity in S15CK, SCM415 and SK5 steels due to temperature cycling under loading was studied in terms of elongation to fracture, m-value and microstructure of specimen fractured. Specimens subjected to constant tensile applied stress were thermal cycled through the austenite (A)\
ightleftarrowsferrite(F)+pearlite(P) or A\
ightleftarrowsP transformation. Main results obtained are as follows. (1) As the applied stress σ decreases, the strain rate sensitivity m increases. The increase of elongation to fracture due to temperature cycling is in a good agreement with that of m-value. (2) Elongations over 500% are observed on specimens thermal cycled to failure in the condition of m-value larger than 0.7. (3) The specimen elongated largely under the small applied stress, where high m-value prevents necking, is fractured with the formation and the interlinkage of many voids. The occurrence of large necking causes the specimen to fracture with smaller elongation because of low m-value under the large applied stress. The true strain per cycle increases corresponding to the occurrence of necking or probably to the formation of many voids.
The effect of salt composition on the Na2SO4-NaCl induced hot corrosion of pure nickel was examined by modified coating and whole immersion tests in still air. The NaCl content of the mixed salt was varied from 0 to 100 mass percent. The corrosion loss and the depth of penetration were measured. The result of coating test showed that corrosion losses were very large at salt compositions from 0 to 25%NaCl and decreased with increasing NaCl content. Corrosion losses by the mixed salt in the whole immersion test were much smaller than those in the coating test. Catastrophic corrosion of pure nickel occurred only in the condition where molten Na2SO4 existed and oxygen was supplied sufficiently. Hot corrosion by NaCl was promoted through the dissolution of nickel metal into molten salt. Except for the corrosion by 100%NaCl, internal penetrations were observed. The depths of internal penetration were almost independent of both the salt composition and test method. The internal penetration was caused by diffusion of sulfur, and proceeded in grain boundaries at an early stage and then within grains. Hot corrosion behavior of pure nickel was the process controlled mainly by the action of Na2SO4 in the salt mixtures.
The effect of the salt composition on the Na2SO4-NaCl induced hot corrosion of Ni-5Cr, -10Cr and -20Cr binary alloys was examined by modified coating test in still air in a temperature range from 1173 to 1373 K. The corrosion loss and the depth of penetration were measured, and the role of NaCl in corrosion by Na2SO4 and the effect of chromium content on corrosion of nickel were discussed. Corrosion losses of Ni-Cr alloys showed the smallest values at 100%Na2SO4 and increased gradually with increasing NaCl content, then indicated a maximum value at 100%NaCl, with the exception of Ni-5Cr alloys at higher temperatures. Corrosion loss of the Ni-5Cr alloy at 1373 K was very large at Na2SO4-rich salt compositions and decreased with increasing NaCl content. This behavior was very similar to that of pure nickel. The total depth of penetration of Ni-Cr alloys increased with increasing NaCl content and had maximum values at the salt compositions of 50-75%NaCl. Addition of NaCl to Na2SO4 accelerated internal penetration. In an internal penetration layer, there existed chromium sulfides only in grain boundaries at 100%Na2SO4, and chromium sulfides particles also dispersed within grains at Na2SO4-NaCl mixtures. Corrosion products were composed of NiO, Cr2O3 and NiCr2O4, and NiO increased in quantity with NaCl content. NaCl promoted spalling of scales. At Na2SO4-rich salt compositions, an addition of chromium markedly suppressed accelerated oxidation of nickel, but it became less effective with increasing NaCl content. While chromium addition was still effective even at 75%NaCl mixture, no effect was obtained at 100%NaCl.
This study was performed to obtain the concentration of defects and the activities of components in wustite doped with MeO(Me: Ca, Sr and Ba). The composition as FeO-Fe2⁄3O-MeO for wustite in equilibrium with CO-CO2 gas mixtures of PCO2⁄PCO=30⁄70, 50⁄50 and 60⁄40 at each temperature of 1273, 1373 and 1473 K, was determined by an analysing method utilizing the weight loss during reduction. The concentration of cation vacancy (VFe\varparallel) is estimated as one-third of the mole fraction of Fe2⁄3O. The value of (VFe\varparallel) increases with an increase in the amount of MeO and in the ionic radius of Me except for the higher concentrations of CaO. The increase in the value of (VFe\varparallel) may be interpreted qualitatively by considering that the strain generated due to the difference in radius in the substitutional dissolution of MeO can be relieved by the formation of an association [MeFe×·VFe\varparallel]. Furthermore, the activities of FeO and MeO were estimated by Schumann’s method from the oxygen pressure contours for wustite doped with CaO at 1273 K.
This paper discusses TLP (Transient Liquid Phase) bonding for heat resistant steels, SUS304 and 12Cr-Mo-V-W steel. Two specially designed Fe-base interlayer alloys, which were produced by rapid quenching from the liquid state, were used in this experiment. SUS304 TLP bonds using 15.7Cr-6Ni-2.8B-Fe interlayer alloy show microstructure and composition equivalent to those for the base metal. Also, the TLP bonds mechanical properties are superior to bonds using commercial Ni-base interlayer alloy (15.0Cr-4.0B-Ni). 12Cr-Mo-V-W steel TLP bonds using 12.0Cr-3.8B-Fe interlayer alloy show almost the same martensite structure as the base metal in contrast to that for Ni-base interlayer alloy, which remains austenitic, even after being diffusion treated at 1323 K for 172.8 ks. Hardness and stress-rupture properties for the bounds using Fe-base interlayer alloy are also equal to those for the base metal.
The effect of fiber arrangements on the thermal expansion coefficient, the Young’s modulus and the Poisson’s ratio of copper-carbon fiber composite was studied. Results obtained in this study were as follows: (1) The average linear thermal expansion coefficient of the composite in the range from room temperature to 473 K became smaller as the volume of carbon fiber increased. The thermal expansion coefficient of the composite containing high modulus carbon fiber was smaller than that of the composite containing high strength carbon fiber. The effectiveness of fiber arrangements in reducing the thermal expansion coefficient was in the decreasing order of the 1) unidirectional, 2) spiral, 3) bidirectional and 4) plain weaving arrangement. (2) The Young’s modulus of the composite which contained high modulus carbon fiber was greater than that of the composite containing high strength carbon fiber. The Young’s modulus parallel to the fiber direction of the unidirectional composite was in proportion to the fiber content. Young’s modulus perpendicular to the fiber direction, on the other hand, decreased as the fiber content increased. The Young’s modulus of bidirectional and weave composites had a weak relation to the fiber content. (3) The above results were predictable from a careful application of the “rule of mixtures” for composites. (4) The Poisson’s ratio of the composite became smaller as the volume of carbon fibers increased. The effectiveness of fiber arrangements in reducing Poisson’s ratio was in the increasing order of the 1) parallel to the fiber direction of the unidirectioal, 2) bidirectional, 3) plain weaving and 4) perpendicular to the fiber direction of the unidirectional arrangement. (5) In the thermal fatigue tests, no degradation in the thermal expansion coefficient of this composite was observed.