The phenomena of sputtering due to glow-discharge and ion-bombardment have been investigated by many workers. The research of thin films for semi-conductor materials has also been developed by means of the reactive sputtering and ion-implantation. In our studies, the changes on surfaces of alloy steels have been observed after the ion-bombardment of moderate energy under the atmosphere of reactive gas. In the present work, the nitriding phenomena are studied on the iron and steels ion-bombarded in nitrogen at voltages 4∼10 kV by hardness measurement, microstructure observation, and electron-diffraction. The hardness increases with the growth of Fe4N, AlN and CrN which are formed by preferential nitriding of the impurities in steels. The temperature of specimens increases with the increase in bombarding voltage and then the hardness also increases up to the temperatures of 500∼570°C at voltages of 5∼6 kV. This is similar to the ordinary nitriding. On cooling, of the specimens, the hardness on the surface indicates a peak in the oblique direction with inclinations 4∼5 degrees from the bombarding center. This result agreed with the experimental data of sputtering yield. For the penetrating depth, the peak of hardness is under the depth of 0.10 mm, and the peak decreases in height and becomes broader in width with the bombarding time. This shows that the penetration of nitrogen is due to channeling at first and then diffusion, in the same way as evidenced by the experimental results of the implantation of semi-conductor materials and the radiation damage by neutron bombardment.
Investigation on the growth process of G.P.zones in a binary Al-6.8 at%Zn alloy was carried out by means of the X-ray small-angle scattering method. By applying the Lifshitz-Wagner theory to the zone growth, the diffusion coefficients (D) and the migration energy (Em) of the solute atoms were determined to be (10−15∼10−14) cm2/sec and (0.38±0.04) eV, respectively, over the temperature range of −17∼40°C. These values were shown to coincide with the ones obtained by the other authors. Also, the diffusion coefficients and migration energies of the alloys containing small amounts of silver, silicon or magnesium were determined. The values of D of the alloys containing Ag or Mg were small compared with that of a binary alloy, whereas the addition of Si had no remarkable effect on them. However, the value of Em of each ternary alloy was larger than that of a binary alloy.
We have studied the precipitation of carbide or nitride from the super-saturated solid solution by the internal friction method. The ageing exponent (n) and the time constant (τ) were determined on the basis of the equation, W=1−exp[−(t⁄τ)n]. Transformation-time-temperature (TTT) curves were obtained from the isothermal precipitation curves of the Fe-C and Fe-N alloys. It was the most significant difference in the two alloys that the rate of precipitation of the stable phase in the Fe-C alloy is much faster than that in the Fe-N alloy. In the Fe-N alloys, the meta-stable phase precipitated at 150°C was completely resolved by an up-quenching to 260°C which is somewhat lower than the solvus temperature of that specimen (270°C). The precipitates formed at 150°C were completely resolved by the up-quenching to 300∼370°C. The overshooting phenomena observed in all reversion curves of the Fe-N alloys appeared to be caused by both the evaporation of small precipitates and the partial resolution of precipitate.
We have studied the process of the strain ageing and the reversion of the meta-stable phase precipitated from the super-saturated solid solution by the internal friction method. The degree of strain ageing was accelerated and the ageing curve shifted to the side of short ageing time by the increase of strain. From changes of the exponent (n) determined on the basis of the equation, W=1−exp[−(t⁄τ)n], the process of the strain ageing was able to separate into two stages. The non-reversional internal friction obtained from the reversion treatment increased with the increase of strain. The meta-stable phase precipitated in the 2nd stage of strain ageing was completely resolved by an up-quenching treatment. All changes of the internal friction was separated into two stages by the level of the up-quenched internal friction value. The changes of the internal friction in each stage was normalized, and the ageing exponents (n1,n2) and the time constants (τ1,τ2) were determined respectively. This technique of the two stage separation of the strain ageing curve based on the reversion treatment seemed to be more reasonable compared to the other conventional methods. A relationship of ρ\fallingdotseq6.31×108×ε1.88 was obtained between the quantity of the strain (ε) and the dislocation density (ρ). The atmosphere density calculated from both the non-reversional internal friction and the dislocation density was about 1∼3 atoms per atom plane threading the edge dislocation line. The binding energy between the dislocation and the N atom of 0.4 eV was determined from the experiments in the decay of atmosphere.
A new method for X-ray determination of the volume fraction of phases coexisting in a sample has been developed. This method is chracterized by accurate and rapid determination of them by analysing a diffraction line from each phase regardless of their grain sizes and their distribution in the matrix. The method was applied to evaluate the volume fraction of the retained austenite in carbon steels in comparison with the results obtained from the known method of measuring many diffraction lines arrising from each phase in the matrix. It was confirmed from the results that the present method is useful to determine rapidly and accurately the volume fraction of phases in alloy materials.
An austenitic 18-8 stainless steel was tested in tension under hydrostatic pressure and the influence of hydrostatic pressure on its stress-strain behaviour was discussed. Tensile tests under constant pressures of 12000 kg/cm2 and atmospheric pressure and tests during which the ambient pressure was changed from 12000 kg/cm2 to atmospheric pressure and vice versa were carried out at room temperature. Also, the change in inductance of a coil wound around the specimen was measured to evaluate the amount of α-martensite induced by plastic deformation. The results obtained are as follows: (1) Pressurizing at 12000 kg/cm2 gives no effect on the stress-strain relation of annealed specimen at atmospheric pressure. (2) By the magnetic measurement, α-martensite cannot be observed in the strain range less than about 10% strain. At a larger strain it begins to be induced and its amount increases with increasing strain by the same rate under both 12000 kg/cm2 and atmospheric pressure. But ε-martensite is observed by X-ray diffraction when the specimen is deformed under 12000 kg/cm2. (3) When the specimens are deformed under a constant pressure of 12000 kg/cm2, the increase in flow stress as compared with that at atmospheric pressure is very large at the beginning of deformation, decreases with increasing strain, and then becomes almost constant (about 12%) above about 15% strain or more. (4) When the ambient pressure is changed between atmospheric pressure and 12000 kg/cm2 on the way of deformation, the flow stress changes 0 to 4% at small strains and, about 12% (pressure raising) and 19% (pressure releasing) at 30 to 40% strain. (5) The phenomena mentioned above in (3) and (4) can be explained by the fact that ε-martensite is induced rapidly at the beginning of deformation resulting in work-hardening under high hydrostatic pressure, while it easily transforms to α-martensite under a low tensile stress at atmospheric pressure at large strains.
Some metallurgical experiments including measurement of thickness change of coated layers and base alloy, microhardness test, microscopic examination, X-ray diffraction analysis, and electron probe X-ray microanalysis were made to determine the composition and the structure of the alloy layer formed on stainless steels, which were dipped in molten aluminum. The results obtained are as follows. (1) In austenitic stainless steels and iron alloys containing Cr or Ni more than about 20%, the alloy layer consisted of thin pure alloy layer and the mixed layer which was a mixture of Al and FeAl3 type alloy. And Cr or Ni had a little solubility in this mixed layer. (2) In ferritic stainless steel the alloy layer had the same structure as that of carbon steels. Namely, it was composed of thin FeAl3 and Fe2Al5 type alloy layer. There was an apreciable solubility of Cr in the latter layer. (3) The mechanism of formation of the mixed layer was also discussed.
In a previous paper, the reason for high recrystallization temperature in Cu-Cr, Cu-Zr and Cu-Zr-Cr alloys was considered to be due to the formation of fine precipitates during recrystallization, which obstructed dislocation climbing or sliding and grain boundary migration. In the present paper, the recrystallization behaviours in Cu-Cr, Cu-Zr and Cu-Zr-Cr alloys quenched, tempered (at 350, 450, 500, 550 and 700°C), heavily cold worked and annealed at various temperatures were studied by the resistmetric method, measurements of mechanical properties and transmission electron microscopy. No fine precipitates were detected at dislocations or sub-boundaries in the low temperature annealing stage, but fine precipitates, which retard recovery, must exist since electrical resistivity decreased by low temperature annealing. The mechanism of retardation of recovery is due to the binding of dislocation jogs and fine precipitates. In the high annealing temperature stage, the growth of precipitates and crystal grains was observed by transmission electron microscopy, and the effect of precipitates on retardation of recrystallization was also detected. The size of precipitates by tempering before cold working did not affect the recrystallization temperature, because the precipitates were sheared by heavy cold working and became a constant size.
In order to study the rolling wear of gray cast iron accompanied by sliding, the mild wear tests were carried out under the dry condition using the upper and lower test pieces of gray cast iron of the same quality. A modified Amsler wear testing machine was used with the load of 3∼60 kg, and at the sliding velocity of 0∼0.27 m/sec combinating the test pieces of various diameters. Results are summarized as follows. (1) The wear process within this experimental limits is understood as the oxidative wear, and the mechanical wear, or mixed, but does not lead to the scuffing. (2) There is a critical point (P=14 kg/mm2) between the wear loss and the stress (maximum Hertz stress), and the wear loss shows a rapid rate of increase beyond it. (3) At the stress higher than 11 kg/mm2, the amount of wear loss of the lower piece is greater than that of the upper one. (4) Chemical analysis of wear particles by means of X-ray diffractometer shows that the amount of Fe2O3 is larger than 50% in weight in the oxidative region, 10∼50% in the transient region and almost zero in the mechanical region.
A new etchant, containing cupric chloride, is described for producing dislocation etch pits on lithium fluoride. It is shown that etch pits with edges parallel to 〈100〉 and 〈110〉 directions on the (100) surface of lithium fluoride can be obtained by using this etchant. The morphology of etch pits, produced by solutions varying the concentration of cupric chloride, pH, the undersaturation and the concentration of chloride ion, has been investigated by the differential interference microscopy and the molecular structure of Cu(II) complex in etchants by the ultraviolet visible absorption spectra. The reason for the change in the etch pit morphology is explained on the basis of the changes in the structure of Cu(II) complex in solutions and in the movement velocity of kinks and steps on the surface of lithium fluoride.
Some etchants, containing ferric ions coordinated with water molecules, thiocyanate, or cyanide ions, are used for producing dislocation etch pits on lithium fluoride. Etch pits cannot be obtained by using an etchant containing [Fe(CN)6]3− ion only as an inhibitor, but can be produced by etchants consisting of ferric ions coordinated with water molecules or thiocyanate ions which bond with ferric ion weaker than fluoride ions. The ultraviolet visible absorption spectra of the surface Fe(III) complex adsorbed on the (100) surface of lithium fluoride are measured, and this complex is suggested to be [FeF6]3−. Screw and edge dislocation etch pits are observed by the scanning electron microscope.
As a series of basic investigation for wet metallurgy of the sulfide ore, galena was selected, which formes an insoluble film on its surface in acidic solution, and the aqueous oxidation properties of galena were studied in acidic solution. Electrolyte used was hydrochloric acid solution with pH 1∼5.7 which was deaerated with nitrogen gas. The dissolution behavior of the galena electrode was measured by means of the galvanostatic and potentiodynamic methods. The anodic film formed on galena electrode in the solution was analyzed by E.P.M.A. (electron probe microanalyzer) and electrondiffraction. The experimental results obtained are as follows: (1) In leaching, polarization resistance (Rp) turns out to be the best parameter indicating the dissolution behavior of galena in the solution. With lowering pH and elevating temperature, Rp decreased slightly. On the other hand, an increase of the chloride ion concentration results in a remarkable decrease of Rp whereby the dissolution of galena is accelerated remarkably. (2) The polarization behavior of the galena electrode in the solution shows a typical active-passive curve. In a basic potential region, the anodic surface film formed on the surface is amorphous sulfur and changes to a mixture composition of S°+PbSO4 at a noble potential. In appearance, the anodic film shows a characteristic behavior of ionic conductors, and the reaction of surface film formation is the diffusion control of lead ron.
Effects of heat treatment on the width of the precipitate-free zone (PFZ) along the grain boundaries in an Al-6 wt%Zn-1.2 wt%Mg alloy have been investigated by means of the transmission electron microscopy and causes of the development of the PFZ have been discussed. The width of the PFZ decreases in the early stages of ageing after water- and direct-quenching and increases again in the later stages. Two-step ageing, in which the first ageing is carried out at a temperature higher than the second, brings about the reduction of the width of the PFZ. Quench-interruption at 200°C before ageing at 120°C results in the development of the wider PFZ. A fine scale dispersion of the precipitates is obtained by ageing after the quench-interruption at 200°C for 3-300 min, as well as after water-quenching, leading to the conclusion that the nucleation of the precipitates does not require either of the G.P.zones and excess vacancies. The results on the PFZ and the precipitate dispersion can be fully interpreted by the precipitate nucleation mechanisms based on the homogeneous nucleation in the matrix and the heterogeneous nucleation on the dislocation loops formed by condensation of the quenched-in vacancies. Thus it has been concluded that the low density of the dislocation loops as the preferential nucleation sites and lowering of the solute concentration near the grain boundaries are both responsible for the appearance of the PFZ in this alloy.
Tension-compression fatigue tests were conducted at room temperature, −196°C and −269°C for 18-8 stainless steel which is widely used as structural materials for cryogenic appliances, using a fatigue testing apparatus specially designed for cryogenic use. As a result, electron microscopy of the fracture surfaces and martensitic transformation near the fracture surfaces were discussed. The results may be summarized as follows. (1) In the range up to 106 times of stress repetition, the endurance limit is not observed on the S-N curve at any temperatures tested. The curve at −269°C almost coincides with the curve at −196°C. (2) On the fracture surfaces at −269°C, parts of smooth surfaces are found near to starting points of fatigue cracks in many cases, which are thought to be formed with rubbing of the crack surfaces; and some scratches like a nail-mark are observed here and there on these parts. (3) Almost no martensite is formed in the specimens tested at room temperature, but small amount of ε′ martensite and considerably large amount of α′ martensite are formed in the parallel portions and the parts near to fracture surfaces of the specimens tested at −196°C and −269°C. (4) The amount of α′ martensite formed increases with the increase of stress amplitude at the temperatures tested. The amount of α′ martensite formed in the parallel portions of the specimens which did not fracture even after 106 times of stress repetition is a little less than the amount of α′ martensite formed in the parts near to fracture surfaces of the spcimens fractured.
When Pt, Pd and Rh contacts are operated in a make-and-break action under certain environments, some black powdery products other than the frictional polymer are sometimes generated at the contact spot and the contact resistance is increased. In order to investigate the origin of increase in the contact resistance, these contacts were operated in N2-O2-H2O-C6H6, CH3OH enviroments by the special tester, and then measurments of the contact resistance, observation of the contact surface and analysis by E.P.M.A. were conducted. The results are as follows: (1) Although the contact resistance of the metals operated in the atmosphere of the laboratory is low and stable, it operated in purified air is increased remarkably. (2) The cause of the increase in the contact resistance in purified air is the oxidation of the metals by mechanochemical reaction. (3) Water vapor and organic vapor such as C6H6 and CH3OH act as the inhibitor of the oxidation by a mechanochemical reaction; it is a cause of the low contact resistance in air not purified. (4) The cause of effect as the inhibitor is the adsorption of H2O and organic vapor on the surface of the contact.
The effects of initial dislocation density and crystal size on the yielding of copper crystals were examined. Dimensions of the specimens used in the present work were 4∼7×4∼7×50∼60 mm3 for the large crystals, and 1.2∼2.7×0.3∼0.9×10.8∼26.9 mm3 for the thin crystals. Thermal cyclic annealing technique was employed to control the initial dislocation density between 7×102/cm2 and 5×103/cm2. The principal results were as follows. (1) Yield stresses of the large crystals were about 10 g/mm2, independently of the initial dislocation density. (2) On the contrary, the yield stresses of the thin crystals were not settled down at a certain value but distributed between 8.3 and 87 g/mm2. (3) The characteristic sharp drop in load and strong coarse slip bands were observed in the yielding of the thin crystals with very high yield stresses. From the above results, it was concluded that the yield stresses of the copper crystals with low dislocation density were probably connected with the cross-over stress of the dislocation dipoles with large height formed before yielding and the stress at which active dislocation multiplications proceed towards the non-slip regions.
The self-diffusion coefficients of silver in molten silver-indium alloys have been measured by the capillary reservoir technique with 110mAg as the radioactive tracer over the temperature range 502∼1144°C. The results are represented by the following equations: (This article is not displayable. Please see full text pdf.) As the diffusate is the same, the volumes of the hole are evaluated from Frenkel’s treatment on the activation energy and are discussed. For the molten silver-indium alloys in which silver is infinitely dilute, the ratio of the self-diffusion coefficient of solute to that of solvent is explained by Swalin’s fluctuation theory.
By applying vacuum-deposition techniques, it may be possible to prepare solid solution alloys made up of constituent elements which are mutually insoluble in the liquid state. From this point of view, Cu-C alloys up to 0.25%Cu were succesfully produced, and their structures and the changes by annealing were investigated. The following results were obtained: (1) By using a substrate held at −196°C, ultra-fine polycrystals having grains of 100∼300 Å in diameter were prepared. (2) These foils held at −196°C recovered. The process of recovery in copper foil may be a type of 1st order reaction, but those in Cu-C alloy foils were analysed to be of 2nd order reaction. (3) The ultra-fine polycrystalline foils were recrystallized at 50∼110°C. The activation energies were 20∼25 kcal/mol and the values increased with carbon content. (4) The recrystallization in foils was considered to progress by two-dimensional growth. (5) The 0.2%-proof stress of Cu-C alloys after anealed at 800°C was about 30 kg/mm2.