Intergranular cracks at high temperatures are classified into two groups, i. e., the wedge type and the cavity type. The former is sharp and long, and is considered to grow by grain boundary sliding. The latter is round in shape, and is thought to grow by diffusion. The present work shows that, by taking into account both grain boundary and surface diffusion, a crack of the cavity type can grow laterally flat along a grain boundary which is normal to tensile stress. The effect of strain energy which is negligible when the spherical growth is assumed must come into the estimation in the present treatment. The lateral growth is feasible especially when the wedge type cracking by grain boundary sliding is prohibited by coarse grain boundary precipitates and hence a high stress is applied. For usual structures without such coarse grain boundary precipitates, when cavities grow to a certain size which depends on the applied stress, they begin to become flat, linking each other more rapidly than in the case in which the spherical growth is assumed to continue. Effects of the gas content and the resistance to creep on the cavity growth are discussed.
Correlation between the activating dissolution behavior of pure aluminium and alkaline corrodents are studied by means of the potentiodynamic polarization method and the potentiostatic immersion method. Corrodents used are of various concentration of NaOH and NaOH+NaCl solutions. Those solutions are deaerated with nitrogen gas and not stirred. The experimental results obtained are as follows. (1) The potentiodynamic anodic polarization curve in the stagnant solution shows a typical active-passive transition and at a critical potential there occurs an activating dissolution of aluminium with a rapid increase in anodic current. (2) The limiting anodic current increases proportionally with the activity of NaOH. When the concentration of NaOH is constant, it decreases proportionally with increasing concentration of NaCl and increases with increasing temperature. (3) The critical activating potential depend upon the activity of NaCl and NaOH. When the activity of NaCl is increased, the critical potential is shifted toward a more basic potential side. But in case of NaOH solutions, it’s potential is shifted toward the noble potential side proportionally with the activity of NaOH. And the change in critical potential value of aluminium is independent of temperature. (4) With the advance of the activating dissolution, the amount of Al3+ ions increases and the value of pH decreases near the electrode interface.
Thin metallic films deposited by the electrochemical method are of increasing importance. The electrolyte composition and the film thickness are very important among the various factors influencing magnetic properties of thin electrodeposited alloy films. The purpose of the present work was to study the relation between the electrolyte composition and the film thickness for obtaining a thin 81%Ni Permalloy film and magnetic properties of the films with varying thickness. The films deposited in the early stage of deposition were found to be enriched in iron. The iron content decreases with thickness, approaching a steady value determined by the electrolyte composition used. The thickness at which each deposit has the composition of Permalloy, therefore, varies with the amount of FeSO4·7H2O in the electrolyte; the amount of FeSO4·7H2O in a typical electrolyte was determined in the range 700∼2500 Å. It was also ascertained that these results were not influenced by metal species of the substrate. A similar behaviour was also shown by the vacuum deposition of Permalloy, the films deposited in the early stage of deposition being enriched in iron.
The physical and electronic properties of the Cd3As2-ZnSnAs2 system have been investigated. Various alloys of the system were prepared by slow cooling to room temperature after direct melting of the combining elements (purity 99.999% up) in stoichiometric proportions in a fused quartz ampoule. Some of these were first annealed to attain an equilibrium state at a given temperature and then quenched. A phase diagram of the system was proposed on the basis of differential thermal analysis. The alloys were investigated by X-ray powder diffraction, electron probe microanalysis, optical microscopy and measurements of microhardness. Furthermore, Hall coefficient, electrical resistivity, Seebeck coefficient and thermal conductivity were measured for the alloys prepared by slow cooling. The results are as follows: The Cd3As2-ZnSnAs2 system does not form a pseudobinary system but corresponds to a cross section of the quaternary system containing probably an eutectic reaction. The conductivity type is n in the region of Cd3As2 side and p in the ZnSnAs2 side, reversing the type at the composition between 60 and 90 mol%ZnSnAs2. The electrical properties at room temperature cover the following ranges: resistivity 10−4∼10−2Ω-cm, carrier concentration 1017∼1018 cm−3, carrier mobility 20∼9000 cm2/V·sec. The thermal conductivity at room temperature shows a minimum value of about 0.027 W/cm·deg at a composition between 20 and 40 mol%ZnSnAs2. The figure of merit of the alloys in this system is shown to be of the order of 10−5 deg−1.
For the purpose of developing a high-strength TiC-and Co-rich WC-TiC-TaC-Co alloy, 0.015 to 3.29%Cu was added to 50WC-15TiC-5TaC-30Co alloys, and the effects on the density, particle size, and mechanical properties were studied. Alloys were prepared by ball milling Cu and TiC together and then by adding this dried mixture to the other components, followed by a further ball milling. The following results have been obtained. (1) The density remarkably increases upon addition of 0.015%Cu and reaches a maximum at apporoximately 0.3 to 1%Cu. A further addition decreases the density. (2) The average carbide particle size decreases and then becomes minimum at the corresponding concentrations. A 3.29%Cu addition increases the particle size. (3) A certain amount of Cu added inhibits the growth of (W,Ti,Ta) C particle but has no effects on those of the other carbide particles. (4) The change in carbide-liquid metal wettability due to the Cu addition was considered responsible for the enhancement of density and the reduction of particle size. (5) The behaviour of transverse rupture strength is closely related to those of density and particle size. The maximum strength occurs at approximately 0.3 to 1%Cu added. Similar conclusions have been reached for other compositions of the base alloys.
The effect of applied tensile stress during aging on Ni3Al precipitates in Ni-Al alloy (7.49 wt%Al) which is the fundamental system of Ni-base heat resisting alloys, was studied by means of measurements of the electrical resistance, electron microscope observations and the tensile testing. The results obtained were as follows: (1) The larger the applied tensile stress during aging (400°∼700°C), the more the precipitation of Ni3Al was promoted. (2) Ni3Al precipitated along the same crystal orientation of the matrix, regardless of whether the tensile stress was applied or not during aging. (3) The yield and tensile strength of the specimen aged at 600°C under 2 kg/mm2 tensile stress were higher than that of the specimen aged at the same temperature under no stress, and the elongation to fracture of the former was smaller than that of the latter.
There are many reports on practical problems about the case-hardening of iron and steel by nitriding in fused salts, but there are some unknown points about the mechanism of the reaction of salts and others. In this paper the changes in compositions of pure fused sodium cyanide (NaCN) and cyanate (NaCNO) salts were investigated during heating at 575°C in oxygen or argon atmosphere by means of chemical analysis of the remaining cyanide. Also, the amount of sodium carbonate (Na2CO3) was measured by the gas-chromatographic technique. On the basis of the obtained results, an attempt was made to clarify the behavior of decomposition of the fused salts and also to correlate it with its nitriding effect for steel. The results gained are as follows: (1) NaCNO was decomposed in accordance with the following reaction: (This article is not displayable. Please see full text pdf.) \
oindentIf pieces of iron exist in the salt, the disappearing decomposition rate of NaCNO was accelerated several hundred times. In this case the nitriding of steel can be performed most effectively, because the above reaction (\
efeq1) proceeds on the surface of steel and active nitrogen is much available for that use. (2) With the blow of oxygen gas the following reaction becomes predominant: (This article is not displayable. Please see full text pdf.) \
oindentNevertheless, its nitriding effect is not so strong. (3) The reaction from NaCN to Na2CO3 seems to be a so-called consecutive process producing NaCNO salt as an intermediate product. (4) As the estimation of the nitriding effect is possible from the measurement of CO2 gas evolved during the reaction, the gas-chromatographic technique would be useful to study the reaction in this case.
Previously we reported about a new surface hardening method using B4C-NaOCN. As NaOCN is decomposed to Na2CO3 at about 600°C, we used Na2CO3 and other alkali metal carbonates (K2CO3,BaCO3). This method is as follows: (1) Coating on the specimen heated to about 150°C, followed by boronizing in B4C powder, and (2) boronizing in B4C-alkali metal carbonates mixed powder. In the latter case, the thickest boronized layer is obtained by boronizing in B4C-20%Na2CO3 mixed powder, namely about 0.35 mm at 1000°C for 5 hr. Using the same mixed powder repeatedly, the ability of boronizing is reduced gradually. The characteristics of boronized steels are the same as that boronized by B4C-NaOCN method reported previously. By boronizing of steels at 1000°C for 5 hr, 1.6% in mean linear expansion is observed. Applications of this method to practical machine parts show satisfactory results.
Kobayashi and two of the present authors have previously discovered that nickel-manganese alloys exhibit high permeability in the concentration of less than about 24% manganese and named them Nimalloy. A further study has since been made on the effect of additions of various elements on the properties of nickel-manganese alloys and obtained the highest initial permeability of 53940 and the highest maximum permeability of 270000. In the present paper, the effect of aluminium additions on the properties of nickel-manganese alloys is presented, with the conclusion that the optimum cooling rate to develop the highest value of permeability for each alloy increases in general with increasing aluminium content. The alloy composed of 78.95%Ni, 19.85%Mn and 1.20%Al showed the highest initial permeability of 10780 when cooled at a rate of 400°C/hr from 900°C and the alloy of 78.81%Ni, 19.56%Mn and 1.63%Al exhibited the highest maximum permeability of 73200 when cooled at a rate of 800°C/hr from 900°C; the latter shows a magnetic hysteresis loss of 9.49 erg/cm3/cycle and a coercive force of 0.0121 Oe for the maximum magnetic induction of 2000 G, and a specific electrical resistivity of 61.0 μΩ-cm at 20°C.
Fundamental properties of various WC-TiC-NbC-10%Co alloys (vacuum-sintered at 1400°C for 1 hr) were studied in relation to their carbide compositions and carbon contents, and the results were compared with those of WC-TiC-TaC-Co alloys (WTT alloys) already obtained by the present authors. The results obtained were as follows: (1) The amount of dissolved W in the γ phase which depends on the carbon content was considered to be the same as in WC-Co, WTT alloys, etc., and Nb and Ti hardly dissolved in the γ phase as Ta and Ti in WTT alloys. (2) The total variation of the carbon content of the βt′ phase (WC-TiC-NbC s. s.) in the (WC+βt′+γ) three-phase region increased with increasing niobium carbide content up to 60% in the βt′ phase, contrary to the case of WTT alloys (the total carbon variation decreased with increasing tantalum carbide content). (3) The width of the three-phase region extended with increasing titanium carbide and niobium carbide contents (the width of the three-phase region of WTT alloys depended mainly on the titanium carbide content). (4) The transverse-rupture strength of the alloys lowered with increasing total amounts of titanium and niobium carbides, in contrast with the strength of WTT alloys which was mainly affected by the titanium carbide content. Thus, the strength was much inferior to that of WTT alloys. (5) The change in lattice parameter of the β (70WC-30TiC s.s.)-NbC system obeyed Vegard’s law as confirmed in the β-TaC system. Properties of the alloys such as magnetic saturation, specific gravity, hardness, transverse-rupture strength, etc., varied regularly with the carbon content in the same way as the other cemented carbides as well as WTT alloys.
The blue-brittle behaviour of a mild steel in torsional deformation was examined at strain rates of 1.1×10−3, 3.4×10−2, 3.1×10, 9.0×10 and 1.8×102 sec−1 between room temperature and 700°C. The temperature of the maximum flow stress and the temperature of the minimum strain to failure increased with increasing strain rate. The former was lower than the latter at the lower strain rates of 1.1×10−3 and 3.4×10−2 sec−1, while at the higher strain rates both of the temperatures were nearly eaqual. The relationship between the strain rates and the testing temperatures of the blue-brittleness depends not only on the diffusion coefficients of nitrogen and carbon in α iron, but also on the concentrations of nitrogen and carbon in it. At the higher strain rates, the specimen was heated by the dissipated mechanical energy and the blue-brittleness appeared at a rather low temperature. The blue-brittle behaviour at the lower strain rates, which was observed below about 350°C, may be mainly due to the strain aging by nitrogen atoms.
Microstructure observations, thermal analysis, chemical analysis and X-ray diffraction have been performed on arc or high-frequency induction melted alloys in argon atmosphere, compositions of which lie on the field of two-liquid immiscibility and one-liquid miscibility. The results may be summarized as follows: With increasing silicon the immiscible gap of the field of the Fe-Ca system became narrow and had a critical point at 33%Fe-33%Ca-34%Si, where the two liquid phases become indistinguishable. With increasing silicon content over 34%, only one liquid solution existed over the entire composition range of the alloy system. It was assumed that a quasi-binary eutectic point should appear in the vicinity of 23%Fe-38.5%Ca-38.5%Si for a quasi binary system existing between the binary intermediate compounds CaSi and FeSi. Freezing of alloys involving ternary three-phase equilibrium completed at 1030°C and the composition of this ternary non-variant point lay upon 5%Fe-35%Ca-60%Si. In the field of only one liquid solution there were four primary phase regions of Si, CaSi, FeSi and FeSi2. As morphological features, Si appeared in a rectanglular form, FeSi in a dendritic or spherical form for FeSi, and CaSi and FeSi2 in a band or plate-like form, respectively.
The temperature dependence of the impact extrusion punch pressure for five kinds of carbon steels containing up to 0.52% carbon was investigated at temperatures from 800°C to 1200°C. The initial punch pressure for the α-and γ-range shows different temperature dependences and it varies discontinuously at the α-γ transformation temperature (A1 point). The initial punch pressure pmax for the γ-range is related to the extrusion temperature T(°K) as follows: p_max = A’ lnR exp(B/T), where the parameter B of temperature dependence increases with carbon content and does not change by the extrusion ratio. The above relationship does not hold for the final punch pressure pmin in which the effect of frictional force becomes large. The parameter B for the initial punch pressure is related to the activation energy of deformation ΔH as B=ΔH⁄mk, where k is the Boltzmann constant and m is the parameter of the stress dependence of the strain rate. The dependence of B on carbon content comes from the variation of m value with the carbon content, and the calculated values of activation energy are 37∼32 kcal/mol irrespective of the carbon content. This means that the activation energy for impact extrusion in the γ-range is very small and about one half of that for self-diffusion. It is suggested that the deformation mechanism at an exceedingly high strain rate differs from that for the usual low strain rate deformation, and that the deformation mechanism at low temperature dominates up to a high temperature range in high-rate deformation such as impact extrusion.
A high-temperature cell assembly attached to a Hitachi model EPU-2A spectrophotometer was constructed to measure the absorption spectra of fused salt solutions. The measurable spectrum range of this instrument is 50000 to 5000 cm−1 over the temperature range from 300° to 800°C. Absorption spectra of palladium (II) in fused lithium chloride-potassium chloride eutectic were measured in the spectrum range from 29000 to 10000 cm−1 at various temperatures between 400° and 700°C. Only one absorption band was found at 20200 cm−1 and its molar absorptivity was 315 at 400°C. An increase in temperature caused both a shift of the absorption maximum to a lower wave number and an increase in molar absorptivity. Some discussions on the species of palladium (II) in this solvent are made in comparison of these results and absorption spectra of palladium (II) in aqueous solutions of high chloride concentration.
A study has been made, by using the Shimadzu-A.R.L. X-ray Quantometer, mainly on the analytical precision and the sample preparation in connection with the control analysis of some ferroalloys for cupola operations. The samples for six kinds of ferroalloys are prepared and analyzed under the same conditions. Three to five elements of each kind of ferroalloys are determined simultaneously, i.e. Al, Si, Mn and Fe in ferrosilicon; Si,Fe and Mo in ferromolybdenum; Si, Cr, Mn and Fe in ferrochromium; Mg, Si and Fe in ferrosilicon-magnesium; Si, Mn and Fe in ferromanganese, and Al, Si, Ca, Mn and Fe in calcium-silicon. Samples are prepared by the briquette technique. The amount of the binder is reduced to minimize the decrease in X-ray intensity due to the dilution effect of the matrix; e. g., one g of stearic acid is added to 15 g of each sample. The following conditions are most suitable from the standpoint of rapid analysis: (1) The time for crushing a sample is 2 minutes. (2) The sample briquetting pressure is 60000 pounds/in2. (3) The integral time by the external standard monitor system is 3 minutes. \
oindentUnder these conditions, each of the elements in the six ferroalloys can be determined with a coefficient of variation below 1.7 per cent, with the exception of Si in ferrochromium and ferromanganese. Because the light element Si in ferrochromium and ferromanganese is small in content, its coefficient of variation is several per cent in the integral time of 3 minutes. However, its reproducibility can be improved by lengthening the integral time. The time required for analyzing one sample, including the sample preparation, is about 10 minutes in all the cases.
By using mixed compacts of the Fe-Cu binary system with different Cu contents, a study of the abnormal expansion which appeared at 1083°C in the compacts during sintering was carried out by the dilatometric method and by means of line analysis of the X-ray microanalyser. The results obtained were as follows: (1) Sintering shrinkage starts at about 700°∼800°C on heating, and the starting temperature of shrinkage is lowered with increasing Cu content in the mixed compacts. However, the sintering shrinkage cannot be seen over 900°C, where the iron particles in the compacts become the γ state. (2) So far as the copper particles in the mixed compacts are in a solid state, they cannot diffuse in the iron particles. (3) Liquid copper in the mixed compacts rapidly diffuses in iron powder particles from 1083°C on heating, and then an abnormal expansion originates from the volume expansion caused by the diffusion of copper into the iron matrix including the evolution of hydrogen which takes place in rapid solidification of the molten copper cementing in the iron matrix of γ (fcc) state. The abnormal expansion increases with increasing Cu content up to 8 wt% which is the solid solubility of Cu concentration in γ iron, beyond which the value becomes constant. (4) As a result of the abnormal expansion, dimensions of the compacts at room temperature after isothermal sintering at 1150°C for 1 hr increase up to 8 wt%Cu. However, over this content they decrease with increasing Cu content by sintering in the liquid state. (5) At a cooling rate of 20°C/min γFe-Cu solid solution seems to be supercooled. The supercooled temperature of γ→α transformation gradually falls down with increasing Cu content up to 8 wt%Cu and then becomes constant.
By using mixed compacts of Fe-8 wt%Cu-P ternary alloys with different P contents, a study of the effect of P contents on the elimination of abnormal expansion was carried out by the dilatometric method and by means of line analysis of the X-ray microanalyser, as described in the previous papers, and in this experiment the X-ray diffraction technique was employed. The results obtained were as follows: (1) An abnormal expansion which appeared from 400°C on heating in the mixed compacts over 0.5 wt%P content originates from the heat of formation for Fe-phosphides. However, this type of abnormal expansion cannot be found in a mixed compact of Fe-10 wt%Cu3P pseudobinary system. (2) The upper limiting temperature of α Fe-P solid solution is elevated by the preferential diffusion of phosphorus, subsequently the solid copper particles are facilitated to diffuse in the α solid solution, consequently the liquid copper retained in the mixed compacts on heating over 1083°C are reduced. In this manner the abnormal expansion which appeared from the melting temperature of copper on heating can be eliminated by the addition of phosphorus. (3) At the maximum temperature of 1150°C in this experiment the amount of the γ phase in the sintered compacts decreases with increasing P contents, but the amount of the α phase increases. Enrichment of the α phase region in the compacts results in the uniform distribution of copper in the iron matrix, and facilitate the sintering behaviours. (4) Dimensions of the compacts at room temperature after isothermal sintering at 1150°C for 1 hr decrease with increasing P content up to 0.7 wt%P and then remain constant.
It has been known that the hardenability of plain carbon steel is improved by the “deform-quenching” treatment. We obtained the T-T-T curve from microstructural observations of the following specimens of a drawn steel 0.42%C wire 2.0 mm in diameter: (This article is not displayable. Please see full text pdf.) The following results were obtained from the above experiments. (1) The position of the pearlite nose of 1250Qu moves into the longer time side than that of 900Qu. Although the grain size of Fo-Qu is smaller than that of 1250Qu, the position of the pearlite nose of Fo-Qu is nearly equal to 1250Qu. As the holding time at high temperature increases the position of pearlite nose moves into the shorter time side in case of Fo-1Qu and Fo-10Qu even if the grain size is the same. (2) By forging in the austenite range as in the case of Fo-Qu, Fo-1Qu and Fo-10Qu, the beginning curve of lower bainite transformation moves into the shorter time side. (3) The starting temperature of martensite transformation of 1250Qu is lower than that of 900Qu, and Fo-Qu, Fo-1Qu and Fo-10Qu show a similar tendency. However, the variation of the Ms point with the holding time at the temperature of finishing forging remains unknown under these experiments.