For the purpose of preparing an oxidation resistant coating on molybdenum, a method of Nichrome alloy coatings by electrophoresis was investigated. Nichrome alloy powder or a mixture of Ni/Cr powder was deposited electrophoretically on the molybdenum surface with zein, a protein charged in an organic solvent. The deposits were heat-treated to make deposited powder sintered and more tightly bonded to the substrate. The following results were obtained: (1) Zein charged by cobalt nitrate acted as a carrier as well as a binder of the powders. (2) Concentration-ratio of cobalt nitrate to zein had an effect on the deposition rate and state of the deposits. (3) Coulombic yields of deposition obtained by this method were about one thousand times greater than compared when the same Nichrome alloy was deposited by the usual electrodeposition.
Measurements of the internal friction Q−1 and mechanical properties have been carried out on open-melted Fe-W alloys containing 0∼20%W. The highest Q−1 value of 34×10−3 at room temperature is obtained with an Fe-14%W alloy rapid-cooled after heating at 1200°C for 1 h. The Q−1 value measured at temperature T increases with increasing T, and shows a minimum near T⁄Tc=0.7 (Tc: magnetic transformation temperature). If a static magnetic field H is applied to the specimen, Q−1 shows a two-step decrease with increasing H. The variations of Q−1 and the coercive force Hc with composition and/or heat-treatment are opposite to each other, i.e. the alloys having larger Q−1 exhibit smaller Hc. The mechanical strength of the alloys increases considerably with the W content.
The isothermal oxidation behavior of seven Fe-20Cr alloys with small additions of 0.7 wt%La, Gd, Y, Ti, Zr, Al and Si was studied in air at 1273 K using a thermogravimetric method, X-ray diffraction, electron probe microanalysis and micrography. The additions of these elements resulted in the remarkable improvement of oxidation resistance. In the case of rare-earth and Y additions, which have strong affinity for oxygen, most weight gains occured within the first few hours, the following oxidation rates were asymptotic. In cotrast, the alloys with the other reactive elements showed approximately parabolic weight gains. The extent of beneficial effect of each element on the improvement of oxidation resistance considerably depended on its affinity for oxygen, but the effect of La and Si additions deviated from this tendency. Internal oxidation layers were observed at the scale base in all the oxidized alloys except in the La-containing alloy, which showed the least improvement of oxidation resistance among the alloys investigated in this study. The formation process of internal oxidation layers under low oxygen pressure was discussed on the basis of Wagner’s theory for the transition from the internal to external oxidation. It was shown that these elements had two main beneficial effects on the improvement of oxidation resistance; the stabilization of the main Cr2O3 scale with dissolving the additive element which was followed by a drop in the dissociation oxygen pressure of the scale, and the formation of a dense internal oxidation layer at the scale base under the lowered oxygen pressure. Both effects were supposed to prevent the dissolution and the diffusion process of Fe into the main Cr2O3 scale. It was also considered that the diffusivity of the elements in the alloys would considerably affect the formation process of the dense internal oxidation layer.
The effect of isothermal annealing on the lattice constant of FeCo alloys, quenched from a disordered state, was observed by means of X-ray diffraction. It was found the lattice constant increases in two stages, which indicates the ordering takes place by a vacancy mechanism, first with quenched-in excess vacancies and then with equilibrium ones. A set of phenomenological rate equations, which describe the ordering and the change in vacancy concentration, were applied to analyse the experimental results, and the values for formation and migration energies of vacancies in FeCo were estimated at 91 and 139 kJ/mol, respectively.
The ordering process of iron rich Fe-Al alloys has been investigated at the elevated temperatures using the Mössbauer spectroscopy. In the two-phase state the alloy exhibits the spectra which are characterized by the superposition of the paramagnetic and hyperfine lines at the intermediate temperatures, whereas the single phase alloys only exhibit the general paramagnetic or hyperfine lines. The spectra are computer analyzed by the least squares method in order to obtain the temperature dependence of the internal field, isomer shift and line width, and the results are discussed in connection with the ordering process. The characteristic spectra observed in the two-phase alloy originate from the coexistence of magnetically different phases, namely, the ferromagnetic disordered α and the paramagnetic ordered B2 or DO3. The isomer shift of paramagnetic lines show discontinuous changes at the critical temperatures of the transformation α\
ightleftharpoonsB2 and B2\
Diffusion of mercury, thallium and lead in polycrystalline samples of aluminum was studied by conventional electroplating and RI tracer-sectioning techniques. The results obtained from the deeper regions of samples showed the real bulk diffusion. The temperature dependence of diffusion coefficients are expressed as (This article is not displayable. Please see full text pdf.) \
oindentwhere D and D0 are represented in the unit of m2/s and Q in kJ/mol. Experimental values of ΔQ were compared with theoretical ones obtained from the Le Claire’s theory.
Contents of calcium fluoride in steel making slags and fluorspars were analyzed by determining fluorine using non-destructive 14 MeV neutron activation analysis. A dual sample irradiation assembly was used to irradiate an analytical sample and an external reference sample of a definite amount of calcium fluoride at the same time. Amounts of fluorine were determined from the ratio of counts of photo peak areas of 0.197 MeV energy of 19O calculated by the TPA method in each spectrum of the analytical and the external reference sample. Decay curves of gross counts, bakground counts and photo peak area counts were analyzed by the least square method using 19O, 16N, 18F and 28Al as the factors. The results confirmed that 19O was interfered by only 16N when the counts of photo peak were used for calculation. Experimental conditions obtained from the investigation of the optimum conditions of activation analysis and those obtained from the experimental results of the ratio of photo peak/background were in good agreement. For the actual analytical conditions, however, the sample decay duration longer than the calculated optimum was chosen to decay 16N. Analytical conditions of 30 s for the sample irradiation, 60 s for decay, and 15 s for the measurement were used. Even if the weight of oxygen present in steel making slags is 30 times as much as fluorine, the contribution of 16N on counts of 19O photo peak area was suppressed down to about 4% of the counts using this analytical condition. There was a significant difference between the gradients of the calibration curves made by synthetic steel making slags containing various materials and by calcium fluoride standards which did not contain any other material. Therefore, it is necessary to use the calibration curves for both the group of steel making slags and the group of calucium fluoride and fluorspars. The results obtained by this method were compared with those by the pyro-hydrolytic method showing good agreement in the entire range of fluorine concentrations.
The effects of Zn concentration, strain rate and orientation on the intergranular fracture of α brass bicrystals were investigated. Also, the effects of grain size and cold-working were examined using polycrystalline specimens. The rusults are summarized as follows: (1) No distinct difference in fracture behaviours is observable between in 80/20 brass and in 70/30 brass bicrystals. (2) The transition of fracture mode from transgranular to intergranular in the lower temperature range is strain rate dependent, but that from intergranuar to transgranular fracture in the higher temperature range is not sensitive to the strain rate. (3) If the orientation of each component crystal is chosen in such a way that the secondary slip system is operative from the early stage of deformation, the fracture mostly occurs transgranularly or intergranular fracture is observable only within a very narrow temperature range. (4) It is suggested, therefore, that the deformation in the interior of grains is a dominating factor in the intermediate temperature embrittlement. (5) In α brass polycrystals, fine grained specimens show two ductility minima in the range of intermediate temperature embrittlement, and they are correlated to the deformation behaviour of α brass bicrystals and single crystals.
Deformation and fracture behaviour of α Cu-Zn, α Cu-Al alloys were examined by micro-structural observations. The results are summarized as follows: (1) The distribution of slip bands of 70/30 brass changes remarkably as the deformation temperature is raised. Though the straightness of slip bands does not change upto about 720 K, the distribution of them becomes coarser as the deformation temperature is raised at intermediate temperatures. Also, the deformation structure at high temperatures (above about 720 K) is characterized by subboundaries and recrystallization, however, free dislocations are observed in the regions surrounded by subboundaries. (2) Though remarkable intergranular fractures are observed at the intermediate temperature range, the fractured surfaces show dimple patterns. Also, similar facet structures and dimple arrangements to those observed in α brass bicrystals are found even in α brass and α Cu-Al polycrystals. (3) In high concentrations of alloys planar arrangements and pile ups of dislocations are observed, but cell structures are observed in low concentrations of alloys. (4) All the structural observations correspond to the behaviour of deformation and fracture of the alloys reported in the preceding papers.
Densities of the molten ZnCl2-MCl (M=Li, Na, K, Cs) binary systems on the alkali chloride-rich side have been measured by means of the Archimedean method with two spherical bobs of different sizes made of platinum. From the experimental results obtained in the present work and the density data on the ZnCl2-rich side obtained by Bloom and Weeks with a pycnometer, the composition dependences of the molar volume, excess molar volume, partial molar volume and thermal expansion coefficient of these melts were calculated for the whole composition range. The excess molar volume and the partial molar volume of these binary melts exhibit very complicated behavior with the changes in both temperature and composition. These results may be attributed to the peculiar properties of molten ZnCl2. The thermal expansion coefficients increase markedly with increasing content of MCl in the composition range of 0∼50 mol%MCl and change monotonously in the composition range of 50∼100 mol%MCl. This fact implies that these melts are associated liquids on the ZnCl2-rich side and become ionic ones in the composition range of more than 50 mol%MCl. The change of the species involved in these melts is briefly inferred.
A centrifuge which can apply centrifugal forces up to 1.4∼1.9×104 m/s to aluminum melt has been fabricated. Al-0.14%Ti melts containing TiC particles were subjected to various centrifugal fields at 900°C and it was found that the aluminum grain counted after solidification in the stationary state was coarser with an increase of the centrifugal force applied to the melts. As titanium in solution is not changed by the centrifugal treatments, the grain coarsening of aluminum appears to take place by the sedimentation of some solid nucleating particles in the melts. The sedimented TiC particles were observed at the bottom of the samples after the centrifugal treatments. The ratios of TiC particle number remaining in the melts to the initial one were calculated on the basis of the TiC size distribution measured in the refiner and it is shown that this result is consistent with the tendency of the grain coarsening. It is concluded therefore that the TiC particles dispersed in aluminum melt act as the nucleating agents to cause the refinement of aluminum solidified grains.
An extraordinarily large anelastic strain is observed relating to twinning on an unload-reload cycle during the tensile deformation of fcc alloy crystals. The anelastic behaviour has been examined in detail for Cu-8 at%Ge alloy crystals with particular reference to the dynamic nature of the twin interface. The results are summarized as follows. (1) The large anelastic strain (often more than 10% in shear strain) is observed at the stage of twinning in alloy crystals having high solute concentrations enough to show the pronounced Luders deformation. In such crystals only thin micro-twins are formed, the initiation of which is noticed by the bend point instead of the sharp load drop on the load-elongation curve. (2) The large anelastic strain on the unload-reload cycle is ascribed to the reversible motion of the interface of the thin micro-twins. (3) The stress required to contract the micro-twins on unloading is independent of the deformation temperature. The origin of the contraction stress is the back stress due to twinning dislocations piled-up against the structural barriers which are formed on the critical plane through the Luders deformation. (4) The magnitude of the anelastic strain varies with the crystal orientation, deformation temperature and strain rate. These dependences are explained in terms of the resistive stress for the motion of the twin interface; the orientation dependence results from the variation of the resistive stress related to work hardening, i.e., the variation of dislocation density, while the temperature (or strain rate) dependence mainly arises from the friction due to solute atoms. (5) The twin interface is highly mobile compared with slip dislocations, thereby the anelastic strain being far larger than the Bauschinger strain due to slip.
A quantitative analysis for the iron-base alloys was made by Auger Electron Spectroscopy (AES). The specimens fractured in UHV (ultra high vacuum) were used. A linear relationship between relative peak height IXR for the element X(X=Cr, Ni and Mo) and the atomic percentage CX of the element X in Fe-X alloys was found. Relative sensitivity factor SXFe of the element X to iron was measured experimentally as the proportional constant for the relation between relative peak height IXR and the atomic percentage CX. The composition of alloying elements in Fe-Cr-Mo, Fe-Cr-Ni and Fe-Cr-Ni-Mo alloys was analysed using relative sensitivity factor SXFe. Reasult of AES analyses showed a good coincidence with the chemical analyses.
Surface tensions of liquid Ag-Au and Cu-(Fe, Co, Ni) binary alloys have carefully been measured by the sessile drop method, and the results were compared with the values theoretically derived by use of several previous equations for the surface tension of regular or non-ideal solutions proposed by Guggenheim and other investigators. It was shown that their equations gave good agreement with the experimental data for liquid binary alloys whose heats of mixing were not more than about 2 kJ/mol, exhibiting small deviations from the Raoultian behavior, while it was also recognized that the experimental results did not coincide with the values calculated from their equations for the alloys whose heats of mixing were more than about 4 kJ/mol, even if they are regarded thermodynamically as being regular solutions.