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A GREAT deal of development has already been made in the technique of drawing iron, steel, brass, copper and aluminium, whereas the drawing of light alloys—particularly those, like duralumin, of high strength values is still in need of further development.

The fatigue tests under varying repeated stresses, which consisted of two different bending stresses (the first and second stress waves), were carried out by the specially designed testing machine, using notched specimens of 0.22 and 0.61 per cent carbon steels and super duralumin. These test results were compared with the calculated ones which predict the fatigue life of metallic materials subjected to such varying repeated stresses. And the following are concluded : (1) The analytical fatigue life of 0.22 per cent carbon steel and super duralumin under the varying repeated stresses has a good agreement with the test results. (2) In the case of 0.61 per cent carbon steel, the second stress wave has no influence on the fatigue life, when the ratio of the second stress wave to the first stress wave, λ, is smaller than about 0.8, and the analytical fatigue lives have a good agreement with the test results, only when λ is greater than about 0.8.

The aging behavior of duralumin (17S) and its difference from those of Al-Cu and Al-Mg2Si alloys were investigated by means of a transmission electron microscope, tensile test, and hardness measurement. It was found that the aging process in duralumin up to the maximum hardness was almost the same as that in binary Al-4% Cu alloy, and subsequently occurred an aging process similar to that in Al-Mg2Si alloys. The distribution of precipitates were much finely dispersed than those in the corresponding Al-4% Cu alloy. The finer dispersion of the precipitates were found to cause the maximum hardness of duralumin in high temperature aging.Manganese, which is known to remove unfavorable effects of iron in this alloy, was found to form spherical particles of Al-Mn-Fe compound even in as-quenched state, and it was also found that precipitates were preferentially formed on these particles. The presence of these compound particles had no effects on essential process of aging, but it seemed to be favorable for grain refining. Aging at room temperature caused no change on structure when observed under an electron microscope. However, it allowed moving dislocations to yield irregular forms, which suggest that very fine and dense G. P. zones contributed to yield considerable hardening in room temperature aging.

As an attempt to enhance the strength of age-hardenable Aluminum alloys, the effect of the addition of small amount of Beryllium was investigated whether Be can increase the age-harden- ability of any Al alloy to a considerable extent or can prevent stress-corrosion to make Al-Zn- Mg alloy of more Zn content become practically useful.Firstly, small amount of Be was added to each one of the commercial Al alloys. The effect of the addition of Be was proved to be remarkable in Al-Cu system; where 0.3%Be could increase the strength of 4%Cu alloy up to the level of super Duralmin. However, the effect was found to be less in Al-Cu-Mg system. These results were discussed in relation to the changes occurred in Al-Cu or Al-S (Al5 Cu2 Mg2) diagram when be was added respectively. The corrosion resistance of Al-Cu, Al-Cu-Mg and Al-Zn-Mg alloys could be improved only slightly by the addition of Be and the stress-corrosion characteristic of Al-Zn-Mg alloy was not so much improved as well as its strength when Be was added. The Vickers hardness of Al-Zn-Cu-Mg-Be alloy, containing 8%Zn, 2%Cu, 2%Mg, and 0.2%Be will exceed 150 when aged at room temperature. But more study seems to be necessary to find suitable composition range for industrial use as the workability and stress-corrosion resistance of this system are not yet satisfiable.Secondly, nine binary Al alloys were studied, choosing Zn, Ag, Mg, Sn, Si, Mn, Ni, Sb and Cd as the second element, when 0.5%Be and 0.5%Mg were added respectively. No alloy system. however, was found to have more hardness than 100 in Vickers when fully aged, except Al-Zn-Mg-Be system already considered above. Al-Ag-Mg-Be and Al-Mg-Be system followed, but they are not satisfiable as high-strength Al alloys from the economic point of view.Other Al alloys; Al-Mg-Si, Al-Zn-Cu, Al-Cu-Mn and Al-Mg-Fe, containing 0.2%Be respectively were considered. The second and third system were found to reach the strength of super Duralmin by room-temperature ageing. Therefore, these two systems may be used commercially, if Be will become much less expensive to be got in Japan.In conclusion, several aluminum alloy sy stsms, such as Al-Cu-Be, Al-Cu-Mg-Be, Al-Zn-Cu-Be, Al-Cu-Mn-Be and Al-Zn-Cu-Mg-Be, the last one being the strongest, were found to have enough strength as super Duralumin. It will be an economic problem whether any of these systems can be used in industry. However, it seems to he extremely difficult to enhance the strength of Al alloy by the addition of Beryllium in such an epoch-making wise as in Cu-Be alloy.

With the same apparatus used in the previous experiment(1), the change of hardness of duralumin was observed during the course of fatigue progress under reversed bending, and the effect of aging on the recovery of hardness of the fatigued specimen was also studied. Duralumin was tested in annealed state and in quenched one. In the course of fatigue process under continuous repetitions of stress, the hardness decreases at first and after passing through a minimum it increases with the increase of the number of repetitions. As the number of stress repetitions increases furthermore, the hardness change occurs in, the quite same manner as above, that is, it decreases to a minimum value and afterwards increases gradually with the increase of stress repetition. The initial decrease and the subsequent increase of hardness in the early stage of repetitions are caused by the change in the outer layer of the specimen, and those in the next stage are caused by the change in the inner portion of the specimen. The number of repetitions at which the minimum value of hardness occurs becomes less as the intensity of stress increases. Further, the amount of minimum hardness in the early stage becomes less as the stress intensity increases so, that the hardness increases at the first application of a stress, when it is of a comparatively high intensity. As to the effect of aging at room temperature, on the recovery of hardness of the fatigued specimen, the following results were obtained. After the. application of stress of a constant intensity, the recovery of hardness takes place in two different manners according to the number of repetitions to which the specimen has been subjected, i.e., when the number of repetitions is small, the hardness of a fatigued specimen increases gradually with the lapse of time and becomes constant after a certain time, but when the number of stress repetitions is large, the hardness decreases first quickly and then slowly and at last it attains a constant value. The higher the intensity of stress, the number of repetitions becomes small, by which the decrease of hardness is resulted in the early period of the rest. The author has explained the above changes of hardness under continuous repetitions of stress by a combined effect of the accumulation of internal stress and the loss of stability of structure. He has also explained the hardness change due to aging by a combined effect of the release of internal stress and the recovery of unstable structure.

In this paper, bars having a stringer of metal sheet in the central line, and semi-circular or V-notches on both sides are investigated photoelastically. The bars are made of epoxy resin and stringer of metal sheet (duralumin or copper), which are bonded together with Araldite 121. The bars are experimented under tension with the simple polariscope. The radii (or depths) of these notches of the bars are varied in several values. Consequently, several interesting results are obtained. And then the problem of reinforced bars having a reinforcement of different materials is studied.

1. Steel calipers of the TsNIITMASh system, whose hinge has an adjustable clamping pressure, meet completely the precision requirements in testing 200–700 mm hot forgings made with tolerances specified by GOST (All-Union State Standard) 7062-54. 2. Duralumin calipers of the TsNIITMASh system with a relaxed pressure on their hinge meet the precision requirements in testing 700–1600 mm hot forgings made with tolerances according to GOST 7062-54. 3. Measurements of 700–1600 mm dimensions with calipers of the TsNIITMASh system are always more precise and stable than those made with factory calipers. The negative systematic measurement error of the TsNIITMASh calipers is virtually constant and small, since their measurement effort varies within narrow limits.

The stresses of U-type notched bars with certain inclusions of different materials under tension were investigated photoelastically. The matrix of the bar of epoxy resin and the inclusions of duralumin, epoxy resin, epoxy rubber (epoxy polysulfide copolymer) were bonded together by adhesive medium, and U-type notches were machined on both sides. The models were tested under tension with polariscope, and then the maximum stresses on the boundary of notches were investigated and several interesting results were obtained conclusively.

It has been shown that when ordinary stress-strain (σ-e) diagrams are constructed for 20-mm thick rolled duralumin plate at various temperatures, the alloy behaves like an isotropic material, while a considerable degree of anisotropy is observed in creep testing.

To eliminate nickel from the heat-resisting light alloys, the author has carried out some experiments with alloys of aluminium not containing nickel. Among these alloys, he select the alloy in a series of supper duralumin, or Y alloy in which manganese is substituted for nickel. The alloy has the following nominal composition. Cu 4.0%. Mg 1.0%. Mn 1.0%. Al remainder. The experiments have been carried out not only on the physical and mechanical properties, but on the practical use of the alloy as a part of the aero-engine. These results are fairly good, and therefore the alloy is recognized as the substitute alloy for Y alloy, which can be used for the casting alloy of aero-engine parts.

In the first part of this paper the author derives the mechanism by which the conduction electrons in pure aluminium are scattered when an external field is applied. Applying these results to dilute solid solutions of aluminium, it is possible to predict the change of the resistivity during ageing. Two alloys are considered here : duraluminium and aluminium-silver alloy in two different stages of ageing. In both cases the qualitative predictions of the theory are in agreement with experiment and even the quantitative results seem to be of the right order of magnitude.

From the investigation of the constitution Al-Cu-Mg alloy system the author found the existence of a ternary compound called “S” to be in equilibrium with Al-solution as reported in a previous paper. The age-hardening of Duralumin and 24 type Super-duralumin was considered to occur in the course of the precipitation of this ternary compound from Al-solid solution. To confirm this consideration, the present investigation has been made on rolled Al alloys containing Cu and Mg, and he confirmed the similar phenomena of ageing observed on cast alloys. Immediately after quenching from 500° the change of dilatation on tempering was measured. The alloy containing Cu only showed a marked expansion from about 210° and subsequent contraction from about 280°. This change of dilatation was considered to be due to the separation of CuAl2. But the alloy containing Cu and Mg showed an expansion and contraction below 100° and the marked change of dilatation from 200° due to the precipitation of CuAl2 was also observed in an alloy containing about 0.5%. However, the alloys containing 1.5% of Mg and 4% of Cu did not show the irregular dilatation due to the precipitation of CuAl2. Therefore, the author has concluded that the expansion and contraction below 100° are due to the precipitation of S-compounds. This phenomenon was not found in the specimens aged for 1 week. The effect of a small content of Si upon the ageing of Al-alloy containing Cu 4% and Mg 1.5% was studied on rolled alloys. Si did not accelerate the age-hardening of quenched alloys, but the alloys containing 0.6-0.8% Si showed considerable hardening when they were tempered at 150° for 10 hours. The effect of Si upon such Al alloys was discussed from the constitutions of Al-Cu-Mg-Si alloy system. The difference of the ageing-phenomenon is due to the fact that the equilibrium relation displace to the Al-CuAl2-Mg2Si-Si from Al-CuAl2-S-Mg2Si. This fact was proved by similar dilatation curve of these quenched alloys as those ones containing Cu only.

Explosively generated plane waves were passed through plates of duraluminum, iron, and steels of various compositions and heat treatments. X-cut quartz disks of large diameter-to-thickness ratios (≥5) were used to obtain continuous stress-time profiles of elastic-plastic wave structures associated with yielding. For times less than wave transit time through the disk, the short-circuit current output is directly proportional to the specimen-to-quartz interface stress up to 21 kbar. The incident wave profile in the specimen is then determined from the interface stress-time profile on the basis of an assumed model. Advantages of the technique are excellent time resolution, high sensitivity, and relative simplicity of use. The profiles for duraluminum, normalized SAE 1018 steel, and normalized Armco iron exhibit a relatively slow rise to the yield stress, subsequent stress relaxation, except in duraluminum, and then a gradual rising transition into the plastic wave. In comparison, SAE 4340 and other tool stee...

Theoretical results are presented which relate the Q factors (internal friction) of solid resonators to two loss parameters λi and μi. The latter are assumed to be characteristic of the energy loss in the homogeneous, isotropic material constituting the resonators. Derivations start from the appropriate frequency—or velocity dispersion—equation in which complex elastic constants, λr+jλi and μr+jμi, are substituted. The following cases are treated: torsional, fundamental longitudinal and fundamental bending modes of solid cylinders, and radial modes of solid and hollow spheres. Deviations from constancy of Q are found in regions where velocity dispersion occurs. Computed results are tabulated which show the dependence of Qμ, upon λ1/μ1 (range 0.1–10) and the propagation factor τ (range 0–5 for cylinders); these apply to duralumin. Similar computations are used to interpret experimental results on polystyrene reported by Biesterfeldt, Lange, and Skudrzyk (see reference 22 in text), and an inconsistency is f...

1. Aluminium light alloys are all very weak for sea water corrosion. Even Duralumin, the best rolling alloy, and Silumin, one of the best casting ones, are not good on this point. Some alloys are really non-corrodible but not used due to their inferior mechanical properties and difficulties in casting, rolling or forging A new alloy was invented in our laboratory 6 years ago, industrial researches were completed and the products are now used in some works. It was named “Chlumin” as it contains chromium, but a few per cent of magnesium and iron are also added. A brief description will be given of it in the following pages.2. Non-corrodibility. Castings of Chlumin and of an alloy of composition Cu 8%, Al 92 %, the most common one, both made by metallic mould, were immersed in 5 NaCl solution. Photo. I shows the result after 4 years. Chlumin gave only little deposit retaining even some luster, while, the other was severely corroded precipitating considerable mass of aluminium hydroxide. The machined surfaces of Chlumin and Silumin plates were exposed to air being sprayed by salt water every day. Photo. 2 shows the result after 2 months. Many black spots appeared on Silumin but Chlumin remained bright. This difference was observed also on specimens immersed in sea water for a year. Experiments were next carried out somewhat quantitatively. Specimens were immersed in 5% NaCl solution in separate bottles. The quantity of deposit and the weight decrease of specimen were measured after 40 days. The results are summarized in Fig 1. Chlumin was a little better even than aluminium. Silumin, Y-alloy, Duralumin and all others containing Cu or Zn were attacked severely. The variations of mechanical properties due to corrosions are shown in Fig. 2. Many test pieces of wire were immersed in 5 % NaCl solution and the solution was renewed at times to expose them to air for a day to accelerate the corrosion. Chlumin and aluminium wires, annealed or not, lose scarcely their strength by 5 months' immersion. The elongation decreases in some cases. While, Duralumin, variously heat-treated or not, loses both qualities rapidly. After 3 months the strength reduces to 80 to 20% of the original value and the elongation to 50 to 20%.3. As a casting alloy. The mechanical properties of a cast alloy depend much on casting conditions. Fig. 3 shows the data on ingots made similarly using same metallic mould. Silumin was in perfectly “modified” condition. Chlumin is a little inferior to Y-alloy in strength and yield point but is superior to it in elongation and impact resistance. It is better than Silumin in every respect and is more easy to cast and safe to use as no special process (modification) is wanted on manufacturing. Any complex form can be cast resisting to severe water pressure test. Pistons of internal combustion engine and parts of electric motor have been used for more than a year with better result than Y-alloy.4. As a rolling alloy. Wires of Chlumin are compared with those of pure aluminium and Duralumin in Fig. 4, being annealed at various temperatures. Duralumin aged after quenching from 510°C into water is exeedingly good indeed when annealed at temperatures below 200°, but becomes worse than Chlumin at 300°. Besides, it may not be a safe process of manufacturing to quench an alloy of melting point of 620° from above 500°. It may be very dificult to heat a large article uniformly above 500°. A little over heating will set in local melting, and when the temperature is too low some parts must meet the worst heat-treatment of Fig. 4. Heating on welding will spoil the good properties given by quenching and aging and it is often impossible in practice to quench, the article again.

By means of X-Ray diffraction, hardness test and microscopic examination, the change in structure of an aluminium-copper alloy (3.4% copper) and Duralumin, that have been quenched, in the ageing and tempering at room and higher temperatures ranging from 150° to 350° is studied. In the ageing temperatures between 150° and 200° complete agreement is obtained between the maximum width of diffraction and maximum hardness but there is no broadening of diffraction in spite of marked variation in hardness immediately after quenching, ageing at room temperature, and heating at 150° for one hour. This may be explained as follows: The lattice of the alloy immediately after quenching is in more contracted state in general compared with that of the alloy aged between 150° and 200° due to separation. Any further contraction is accompanied by unproportionately large increase in stress. In other words, it is not difficult to assume that in spite of long time necessary for ageing the actual shifting of the foreign atom is very small, resulting in no practical change in the width of diffraction. On the other hand, in ageing between 150° and 200° there is some separation of the foreign atom, which results less contraction of the lattice as a whole. Under tlhis condition comparatively a large distortion will cause a small stress. Therefore, in order to produce an internal stress of lattice which indicates such degree of hardness as shown in the experiment, rather a large increase in distortion of the lattice must teen accompanied causing an increase in width of diffraction.

This study was made on the changes of the Vickers hardness, the electric resistance, the differential dilatation and the thermal analysis in the artificial age-hardening of, , the 24S type super duralumin SD1 (Cu 4%, Mg 1.6%) and SD2 (Cu 3%, Mg 2.5%). The results can be summarized as follows:- The abnormal changes, observed at the dilatation curve and the thermal change in the ageing at a room temperature, are attributed to the migration of dissolved atoms prior to the precipitation. The abnormal phenomena, which were produced at about 250°C in the course of slow heating, have been assured to be resulted from the precipitation of compound S (or S and CuAl2). The precipitation of compound S and CuAl2 could not be separated to observe in this experiment.

Studies are made on the surface distortions which occur on metal surfaces which have received hardness test indentations from both diamond pyramid and diamond cone indenters. The surface contours are evaluated by multiple-beam interference methods. Experiments are reported for indentations over a wide range of hardness, the surfaces studied being those of sintered tungsten carbide, niekel-steel, duraluminium and tin. The distortions found in polycrystalline masses resemble one another but reveal secondary differences. On single erystallites of tin unsymmetrical patterns are found, with piling-up in two directions and sinking-in in directions at right angles to these. The effects are deternfined by the directions of the crystal axes. The concavity and convexity of the sides of the pyramid indentations axe discussed in relation to piling-up and sinking-in, and the influence of recovery is indicated.

The effects of ultrasonic sawing (frequency 19.7kc, amplitude max 7.5μ) of the aluminum, brass, duralumin, mild steel etc, by using the hack sawing machine, were investigated. The results were as follows : 1) A built-up edge and residual chip were not obsereved in the ultrasonic hack saw even for soft material. 2) The cutting time is decreased to about 1/2∼1/4 of the conventional sawing. 3) This ultrasonic hack saw was able to cut-off the brittle material smoothly, for example tellurium, which is easily cracked by the conventional sawing cutting resistance. 4) It was proved that this ultrasonic hack sawing was a very effective cut-off process.

In this report, the effects of machining or coaled metals on the cutting force and surface roughness etc were invesitgated. The exteriments were performed by the orthogonal and conventional cutting of the mild steel, brass, duralumin cooled by alcohol and liquid nitrogen.(max temperature -60°C) The results were as follows : 1) The cutting force and surface roughness of the mild steel is decreased at about -20°C, but other metals had no changed phenomenon at the room temperature machining.2) At mild steel cutting, the cutting force and surface roughness (about 1μ roughness) at the lower temperature than about -20°C were samed at -20°C.3) It is found that this phenomenon has same ten dency to the impact valve at the low temperature of the mild steel.4) This cold machining method was effective machining to the body centred eubic lattice material, but had no advantage to the face centred cubic lattice material.

Equation of state data for Duralumin in the pressure range from 0.1 to 0.3 megabar have been determined dynamically by measuring shock and free surface velocity electrically in a plate of 24 ST Duralumin that has been stressed by a high explosive detonation. A theory is presented which allows comparison with data obtained by other experimenters, and which yields the relationship between pressure and compression either at constant entropy or constant temperature. The empirical form chosen for the equation of state (p=αμ+βμ2) expresses the pressure as a quadratic function of the compression. Experimental techniques are described in detail. Five points are given for the equation of state of Duralumin in the pressure range from approximately 0.15 megabar to 0.33 megabars. Some data are also presented for cadmium and steel.

The article describes the results of an investigation of the endurance and corrosionfatigue strength of grade-D16AT aluminum-clad duralumin with crater-like corrosion pits. It was established that the fatigue resistance of duralumin decreases with increasing depth and surface area of corrosion-induced defects of this kind.

The dynamic behaviors of super duralumin (24S) have been studied through experiments in which the material in the form of bars was shot from a gun of compressed nitrogen gas at a steel anvil bar. The impact speeds was varied from tens of meters per sec to 190 meters per sec by which the test was made in the range of about 20% strain. The test of the specimens was performed just after the quenching and after the age-hardening for 80min at 100°C. The main results obtained are as follows;(1) By comparison of the dynamic stress-strain curve of which the strain rate is estimated at about 104 1/sec and the static stress-strain curve of which the strain rate is (1∼4)×10-4 1/sec, the sensitivity to the strain rate is hardly recognized in the age-hardened specimen, but is obviously recognized in the specimen fresh following the quenching.(2) It is assumed that even after the age-hardening of the material there will be variation in the internal structure of the specimen due to the nature of the deformation, whether it is static or dynamic. The effect of the variation on flow stress is not obvious till the strain is increased up to about 10%.(3) All the stress-strain curves obtained statically and dynamically of the specimen after age-hardening and those immediately following the quenching are approximately represented by the following equation, σa=σe+C2(ea-σa/E)1/2, where σe: yield stress, E: Young's modulus and C2: constant. It can be recognized in these curves that the stress value extrapolated from these curves at strain 100% is approximate to the characteristically constant value of the material.(4) The relation between the impact speed V1 and the strain e1, V1=∫e10(1/ρdσ/de)1/2 de, is applicable to the range of strain up to about 18% or to the range of impact speed up to about 180 meters per sec of both the specimen fresh following the quenching and of the age-hardened specimen.

An enormous number of duralumin rivets are used in making an aeroplane. As Duralumin is an Aluminium alloy age hardens very quickly after quenching almost of its maximum property, then the riveting work sometimes encounters several inconveniences and is lowerd its efficiencies. The present work is carried out to reduce these troubles. By an addition of Mn more than one percent on the alloy Al+Cu2+Mg2%, the hardening process in the ageing curve at 25° is suppressed about 120 hours after quenching. Above alloy is named D4. Improveing the D4 alloy, a few alloys were obtained as shown in following table. The riveting material invented in “Heinkel” Company is reffered in the same table.

The strength of metals under combined stress, that is, static tension and repeated torsion, has been investigated. K. Hohenemser and W. Prager experimented on mild steel under this stress condition. From their experiments it can be deduced that static tension has an injurious effect on the fatigue strength for torsion. But, considering the combined stress condition theoretically, authors could suppose that, static tension has no effect on the torsional fatigue strength of materials which was, fatigued by shear stress, but it has an injurious effect on those which was fatigued by direct stress. To ascertain the supposition, we made experiments for several materials, that is, mild, medium and hard steels, a cast iron and a duralumin. Mild steel, medium steel and duralumin are materials which are considered to be fatigued by shear stress and cast iron is, on the contrary, fatigued by direct stress approximately, while hard steel is a neutral material of the both two. From our experiments, the following results has been obtained. As we expected, static tension has no effect on mild and medium steels, a very injurious effect on cast iron, and a somewhat injurious effect on hard steel. For mild and medium steels the torsional fatigue limits are even slightly elevated by static tension when the specimens yield by the combined stress of tension and torsion, though the diameters of specimens reduce by yielding. Failed specimen of each material shows a very interesting fracture according to the magnitude of static tension.

A flexibly mounted disc machine has been developed which permits the vibrations excited by rolling contact to be studied in isolation from their surroundings. The principal mode of vibration is a “contact resonance” in which the discs oscillate on the “spring” provided by their elasticity in the vicinity of their point of contact. Vibration in this mode has been observed to lead to the spontaneous generation of corrugations on the surface of the softer disc in two different circumstances : 1. (a) Brass discs, dry or lubricated, progressively developed corrugations by plastic deformation. 2. (b) Duralumin discs, carefully degreased, developed corrugations by ‘stick-slip’ wear when sliding accompanied rolling.

The apparatus used in this work comprises a double photoinultiplier adapter of the variable wavelength type, designed primarily for basic research with quartz prism spectrographs, and an electrical integrator. Details of performance are given for electrical and for photometric measurements and the influence of movements of the light source is considered. The precision of analysis using duralumin alloy with excitation conditions of comparatively large variability, was not found to be significantly higher than by equivalent photographic methods except in the case of silicon at high concentrations and for nickel. The accuracies found were lower than those claimed by other workers using photoelectric methods, the difference being attributed to excitation conditions. It was convenient to use as internal standards lines of high intensity, well separated in wavelength, and this procedure was found to be reliable. The long term reproducibility of the results was worse than the short term value, because of temperature effects. The speed of analysis with the adapter in its primary form was not high when used for determinations of more than one element.

IN the previous chapters consideration has been given generally to aircraft of composite construction in which the main structural members are of timber. In this article it is proposed to deal with aircraft having all‐metal structures, the materials employed in which are in general of steel, duralumin and aluminium.

Studies of the static electrode potentials of the R, Duralumin, M 22, DK and S 2 aluminum base alloys show that these alloys have the same behavior as pure metal in buffer solutions initially free from metal ions within the pH range 1 to 8. The repetitive oscillographic method was used to examine the corrosive action of chloride ions on the anodic behavior of the alloys studied. Oscillograms are presented to show the potentials of the alloys in various pH ranges. Composition of the buffer solutions at various pH levels are given in tables. 6.4.2

Soaking the annealed Al-Cu alloy or duralumin in the nitre-bath heated at 540° or 500° respectively, the solution-velocities of various precipitates in the alloys have been determined rontgenographically. The effect of the rate of dissolution of the precipitates on the aging properties of the alloys has also been investigated. The results obtained may be summarised as follows: (1) The dissolution of CuAl2 at 540° in aluminium takes place at first very rapidly; for instance, it is 80% with the 3 minutes-soaking and nearly 90% with the 10 minutes-soaking. Although no marked difference in hardness of the alloys after aging has been detected, the alloys soaked for a short time in the nitre-bath showed the tendency to harden rapidly during the aging, compared with those soaked for a longer time. (2) In the case of duralumin, the solution-velocities of various precipitates, namely, CuAl2, Mg2Si, Al13 Cu7Mg8, AlMn6, etc., seemed to differ with each other; it is certain that the solution-velocity of Mg2Si is smaller than that of CuAl2. In order to dissolve the precipitates almost completely into a solid solution, the duralumin should be soaked at least for 20 minutes at 500_??_510°

It was required to determine the true stress/true strain behaviour of several alloys, and to relate this behaviour to their fracture characteristics. A device was produced which measured the change in diameter of a tensile specimen during testing. The onset of necking was sensitively detected, and the gauge length minimum diameter measured at intervals up to within 3–5 sec of fracture. True transverse strain was then obtained together with corrected stress. Curves for a number of materials and conditions are given in the paper (naturally and artificially aged Al-Cu-Mg alloys and Al-Zn-Mg-Cu alloy). The necking strains, fracture strains, and strain hardening indices are discussed and the difference in strain hardening of naturally and artificially aged Al-Cu-Mg alloys is shown in terms of these parameters. The differences between commercial duralumin and a super pure ternary compositon are also shown. Metallographie evidence of the sequence of particle cracking and formation of voids up to the point of fracture is also presented in the paper. The effects of such features in commercial alloys, together with grain boundary weakness in the super pure composition are considered.

The effect of the cavity before the membrane in the usual condenser microphone is to cause an increase of pressure at the membrane over that which exists in the undisturbed (free) sound-field, particularly at high frequencies. An approximate theory of the effect is given and a specimen case is calculated. In this case the pressure ratio reaches a maximum of 2.5 at 3000 cycles. Experimental values obtained with the Rayleigh disk are compared with the computations and are in general agreement. A modified design for a condenser microphone without a diaphragm cavity, and adapted for spherical mounting, is described. The temperature coefficient of sensitivity due to the unequal thermal expansions of a duralumin membrane in a steel mounting was found to be 0.6 per cent per degree C. The importance of taking the cavity and reflection effects into consideration in the construction of curves showing the overall fidelity of broadcast transmitters is stressed on account of its intimate relation to the design of radio receivers for uniform frequency response.

An experimental research showing how corrections in the value of velocity of phase propagation may be made to take into account lateral inertia, and how the law (Rayleigh's) will break down at higher frequencies because of other types of vibration intervening. When the ratio of radius to length, multiplied by the mode of vibration [Formula: see text] exceeds a certain figure (in the case of duralumin, 0.55) the law breaks down, and it appears that radial longitudinal vibrations intervene. From the research a simple method emerges to determine Poisson's ratio, which in the case of duralumin is found to be 0.35.An application of this ultrasonic method is made to determine Young's modulus for ice, in order to find more consistent values than those generally quoted. The value of this modulus for ice at about 0 °C. is found to be about 9 × 1010 dynes/cm2. corresponding to a velocity of sound in it of 3.15 × 105 cm. per sec.

The load-elongation diagram of a soft steel tested at the temperature of blue shortness indicates continuous serrations after yield point up to the breaking stage. Although this phenomenon has been widely investigated, no satisfactory cxplanation has yet been given. Moreover, such a serrated deformation is not peculiar for a low carbon steel, as it is observable in some ferrous and non-ferrous alloys tested under a suitable condition. In order to contribute some light for this problem, the present author has studied it with carbon steels of various compositions and structures, some special steels, single cr_??_ stals of iron, duralumin, brass, copper, nickel, aluminium and zinc at temperatures ranging from the liquid nitrogen to the red heat. From these experiments two cases are classified for the serrated elongation. The one case is that when the materials having, to a certain extent, impurities or structural flaws are tested at a proper temperature and under a slow rate, if possible. The other is observable when the metals of high purity are tested at a rate as quickly as possible. These results are explained as follows:- In the fomer case the crystal grains are temporarily brought to an unstable state, by concentrated stress due to notch effect and in the latter case they are brought successively to an unstable state by overstress due to rapid loading and followed by yielding.

It seems to be influential that the process of age-hardening of Al-Cu alloy is associated with the congregation of Cu atoms on the (100) planes of crystal as suggested by Desch (1934) and Preston (1938). As to the cause of artificial age-hardening of the alloy, there are precipitation theories as suggested by Fink and others, but several authors assume that the phenomenon is associated with the congregation of solute atoms within the solid solution. The present author investigated the hardening phenomena of Duralumin, Al-Cu alloy, Lautal and Al-Mg2Si alloy by tempering these aged specimens at various temperatures (180°, 220°, 260° 300° and 350°) for various durations (from 1/1000 to 80 hr.) and measured the hardness and impact value directly after tempering and repeatedly measured subsequent changes in hardness of the specimens with the lapse of time at room temperature. When naturally aged specimens are tempered at above mentioned temperatures, the first effect is the sudden reduction of the hardness accompanied with the increase of impact value and the decrease of electrical resistance. On ageing these softened samples at room temperature, they recover the hardness to the same degrees as that of original specimens accompanied with the decrease of impact value and the increase of electrical resistance, and the author called this phenomenon under the name of “secondary hardening” (denoted by II in Figs.). The phenomenon of sudden reduction o ` hardness on short time tempering may be explained that the congregated solute atoms have gone back into solution before the precipitation of excess solute begins, and the subsequent re covert of hardness is attributed to the re-congregation of solute atoms as the quite same process of natural ageing. Softening and hardening processes may be repeated several times as indicated in the Fig. 20 by the repetitiozl of short time tempering and natural ageing. On the prolonged tempering, the increase of hardness is observed as denoted, by III in Figs. and the author called, this hardening under the name of “temper hardening” according to the suggestion of Prof. K. Honda (1939). With the rise of hardness due to the “temper hardening” boundary precipitations become visible under the microscope, and then the hardness reaches maximum. (III) On further duration of times of tempering, the hardness gradually decreases and the lamellar structure becomes visible under the microscope. On more prolonged tempering, it finally loses the regularity- of lamellar structure and alters its form into small spheroidal particles. The lamellar structure seems to be so called “intermediate” phase as indicated by Guinier and his collaborators (1938), but the maximum hardness takes place prior to the appearance of lamellar structure. The experimental data on age-hardening of Duralumin alloys have led to the following conclusions: 1. There are three hardening phenomena in Duralumin alloys as follows: (a) Primary hardening (natural age-hardening). (b) Secondary hardening. (c) Temper hardening (artificial age-hardening). 2. Primary hardening may be explained by the theory of congregation of solute atoms which are supersaturated by quenching. 3. The mechanism of secondary hardening may be explained by the same theory as that of primary hardening. 4. During the primary and secondary hardening, the reduction of impact value and the rise of electrical resistance are similarly observed. 5. “Temper hardening” occurs on the basis of precipitation of “intermediate” phase or of compounds, but the maximum hardness is attained prior to the appearance of the lamellar structure under the microscope.

The relation between the grain size and mechanical properties of duralumin was studied. It is concluded that the tensile strength of duralumin decreases as the number of grain per unit area decreases, and the resistance to fatigue is also similarly deduced. The fine grained structure is obtained by either one of the following 3 methods. (i) In cold extension, its percentage must be less than 2 or greater than 10. (ii) In hotforging greater the percentage of reduction and lower the temperature of forging, finer the obtained structure. (iii) Increase the percentage of manganese up to 1.2.

A pressure bar gauge is described in which the average stress over the cross-section of the bar is measured by means of an X-cut quartz disk. Bars of duralumin and lead are employed since the acoustic impedances of these materials closely match the value appropriate to longitudinal thickness vibrations in the quartz. The design of a gauge housing, suitable for mounting in the wall of an explosion or shock tube is discussed.

The paper gives an account of the various stages in the development of end-window self-quenching Geiger-Muller counter tubes for the detection of β-particles.Commencing as a tube using the feather-edge type of copper-to-glass seal, one inch in diameter, with a copper-foil end window, the design was later modified to one more suitable for production on a larger scale, employing a standard Kovar/glass eyelet seal, the assembly of all metallic joints being effected by means of soft solder.To permit the detection of slower β-particles, a similar tube was developed having a Duralumin window of thickness 1 mil, which was soldered to an electroplated copper layer. The assembly process was subsequently simplified by use of a thermosetting plastic adhesive wax called “Araldite”.For the detection of very slow β-particles it was necessary to use a mica window of about 0.25-mil thickness, and a suitable seal, using Araldite, was devised for windows of this material.It was found during the course of development that extreme purity of the filling gas and quenching vapour was unnecessary, and less rigorous pumping than that associated with most electronic tubes was also permissible, the most important factors in obtaining good tubes being cleanliness and freedom from loose particles and lint.

Anodic Oxidation of duralumin type Al-Cu-alloys such as 11S, 17S and 24S is regarded to be generally difficult. It is because of the corrosion that sometimes occurs just after the electrolytic treatment of them due to the effect of their copper content. In this study various experimens on 11S have been couducted by changing the conditions of electrolytic treatment, such as of voltage, current density, components of bath, temperature, and time, respectively. As a result, it has been revealed that anodic oxidation could be carried out without any trouble under proper experimental conditions.

研究目的約6年前当時資材入手難から精紡機用チンローラをジュラルミン製ローラ (以下ジュラローラと仮称す) に設計変更し紡績各社で使用して貰った.当時相当是非論があり, 中でも耐久性については疑問視されていたのであるが最近敷島紡績味野工場の実圧結果が判明したので一応纒めて報告する.研究結果(1) 何等特別の不具合もなく6年間使用された.(2) その間チンローラ等に行われている定期的修理は一度もなかった.(3) 各ブロックの中央部に製作当時に比し若干振れが大となる徴候がある.(4) ギャエソドは始動時のトルクのため鋲の弛緩があった.(5) 一部の手直しにより更に十分使用することが出来ることを確認した.(6) 電力の節約が大である.

Nowadays, the method of the continuous casting attracts attention of the aluminum sheet makers because of the best casting method, but the detai1s a re not dear. The authors carried out the experiment of the continuous casting of the 2S slab ingots. The apparatus are used as the same one as the previous report. In the first, the conditions of the casting- casting temperature, casting velocity, deceriding velocity and the cooling velocity-are determined. Next, the crystal structure and the amounts of the segregation are inspected. The results obtained are shown in the table 1, photograph 1, and figure 3.. From these results we can say that the continious casting is a very good method of the 2S slab making but we can't avoid the inverse segregation of the iron if the casting conditions are not properly selected., 近時連続鋳造法が斯界の注目する所となり，特にアルミニウム器物製造各社ではその実施の態勢に入ったので今回は本法によるアルミニウム鋳塊(2S)製造に関する試験結果を報告することにした。従来は主として傾倒式鋳造法により製造されているので両者を比較検討し乍ら報告したい。傾倒式鋳造法による2S鋳塊製造に関しては池野氏の詳細な報告がある。連続鋳造に関する研究報告は我が国では著者等のもの以外は見当らないが外国のものは近年比較的多い。古くはZeerlederがJunghaus法によるDuralumin鋳塊について，その中心，中央，外周の3箇所から分析試料を採取してCuの偏析の程度を調べ連続鋳造によっても偏析は防止出来ないと報告している。G. Siebel, D. Altenpohl, H.M. Cohen等は連続鋳造によるアルミニウム鋳塊では偏析が周期的に生ずることを指摘している。また鋳造条件として湯口の形状を種々挙げ，注湯を開始してから下型を下げ始めるまでに要する時間，言い換れば金型中に存在している湯の高さが偏析に影響することを述べている。B. H. Watersは連続鋳造による鋳塊にはしば～気孔が出来るが，これは鋳造の時ブリッヂが出来た時，凝固の時瓦斯が発生し，その瓦斯と金属が反応した時，鋳造の際瓦斯が機械的に混入した時などで更に鋳造速度に原因する。又下型に注がれた湯の高さが低い程気孔は出来にくいと報告している。R.T. Starples, H. J. Hurstは連続鋳造を正確に実施するためには (1)鋳造温度を一定に維持すること (2)冷却水の温度を±1°～2°に保つこと (3)鋳造温度を測定し得ること (4)型に注入された湯の高さを一定にすることなどが必要条件であると述べている。最近我が国に於て2, 3の連続鋳造装置製造会社が出ているが著者等の装置と大同小異で下型の上下する機構を油圧，水圧にしたもの，注湯の冷却用水槽を持たず，上型の水冷とシャワーだけ乃至上型の水冷だけのもの等である。然し偏析の防止と言う点からすれば底部からの冷却効果を可及的大にしてやる必要があると言う著者等の意見には変りはない。

The author points out the clear distinction which has to be drawn between kinetic and static friction, and describes the special apparatus used in the investigation carried out to determine the static friction of various combinations of metals, including stainless steel and duralumin, under several conditions of dry and viscous lubrication. The paper stresses the effect of time, and gives data showing the rapid growth of the coefficient of friction during the first twenty-four hours at rest, and the subsequent increases over a period of five days. A series of long-term tests of thirty, sixty, and ninety days, on a selected number of specimens, provides a direct comparison from which the relative merits of the various combinations of materials is drawn. Evidence is provided suggesting advantages to be derived from the use of graphite as a preventative of clinging friction. In conclusion, an explanation is put forward as to the possible causes responsible for the building up of friction with the passage of time.

The ageing of super-duralumin (RF1 Cu 4.01%. Mg 1.77% and RF 2 Cu 4.09% Mg 1.12%) and Al-Cu alloy (Cu 2% and 4%) was investigated by X-ray back reflection focussing method using Cu Ka radiation. The quenched specimen was fixed on an X-ray camera and incident X-ray beam was adjusted so as to illuminate the same part of the specimen always from the same direction. Photographs were taken immediately after, quenching, 15min., 30min., 1 hr., etc. and obtained following results. Some of the spots reflected from (511) planes of super-duralumin change their shapes by internal strain or bending of the crystal grains during ageing and this continues for several hours. At first, the change in the position of the spot is rather at random but finally it displaces to the side of larger-lattice constant. The mean dilatation of the lattice after 20 hrs. was 0.0121% and 0.0274% respectively, for RF1 and RF2, while the lattice constants immediately after quenching were 4.036 and 4.035 A. U. Above result confirms that of Nishinmra(1) who found that the natural ageing of super-duralumin is mainly concerned to the formation of ternary compound S or CuAl2. Regarding dilatations of the lattice the present author already observed in the case of duralumin(2). According to Nishimura's ternary diagram the formation of CuAl2 will also take place in RF2, and therefore the dilatation of the lattice of this alloy is larger than the other. The change in the shape of the spot and the displacement of its position is not so remarkable in Al-Cu alloy, but in some alloys having 4% Cu, bending of the atomic plane during ageing was very noticeable; the tendency of lattice dilatation was also observed.

The effect of various aggressive media encountered in agricultural aircraft applications on the fatigue and long-term strength of flat riveted duralumin specimens (simulating the casing of various aircraft parts) was studied. It was shown that crevice corrosion in the zone of contact between various parts leads to a substantial reduction in their fatigue and long-term strength.