Resistance of some of the aluminium alloy sheets to weathering under various conditions in Japan is examined for certain long periods by the Japan Light Metals Soc. associated with laboratories of several universities and manufacturers to contribute to architectural and other usages of alumimum.
The materials to be tested are eleven aluminium alloy sheets such as 1S, 2S, anodized 2S, 24S, alclad 24S, 43S, anodized 43S, 52S, 61S, 63S, and anodized 63S, as well as some aluminium sheets manufactured by Alcan, pure copper, brass and galvanized steel sheets for comparison with these aluminium alloy sheets.
They are exposed to weathering at sixteen locations under different atmospheric conditions in this country for six months, 1 year, 2, 4, 7, 10, 20, 30, 40 and 50 years.
Tensile test and measurement of mean and maximum depths of corrosion-pittings of the sheets are performed after each exposure period in order to determine the mean corrosion-rate of each allay in each location.
This examination will be commeced on December 1, 1955.

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  In the present work, the heat transfer phenomena at the casting-resin-coated sand core interface and the structure of surface layer in casting have been studied using squeeze method with pressure of 0.230 and 820kgf/cm². The heat transfer coefficient and the heat flux at casting-core interface were calculated by the heat balance equation. The surface structure of castings was examined with metallographic method.
  The heat transfer coefficient at the casting-core interface increased with increasing force of applied pressure. The values of heat transfer coefficient at the interface under gravity, 230kgf/cm² and 820kgf/cm² are 0.0005, 0.0015 and 0.0017 cal/ (cm²·s·°C), respectively. The changes of heat transfer coefficient at the interface have been influenced on the condition of contact between castings and core. When the pressure is 0kgf/cm², the surface of castings is rough. Smooth surface is found when the pressure is raised from 0 to 820kgf/cm². In case of 0kgf/cm², the structure of surface layer at the interface are coarse. On the other hand, the microstructure of castings at the interface is fine under pressure of 820kgf/cm². Solidification rate in the castings is extremely rapid and therefore fine chill surface forms. The heat transfer coefficient at the castings-core interface corresponds well with the structure of surface layer of castings.

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  The gases in biscuit, runner, gate, product and overflow portions of aluminum alloy die castings were investigated by mass spectrograph. The gas content was the lowest in the biscuit, and gradually increased in the runner and gate, and abruptly in the product and overflow. The gas of the biscuit contained about 80% hydrogen and 20% nitrogen, but the content ratio of hydrogen to nitrogen in the product portion was reversed, because the molten metal injected through a gate included large amounts of air from die cavity. The gas content and porosity varied from position to position in the product and was the highest in the position near the gate which included more nitrogen than hydrogen.

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  Cutting resistance, cutting temperature and others of pure magnesium and AZ 91 magnesium alloy castings related to the change of cutting speed were examined by an inward face turning under the cutting conditions in Table 2. The cutting speed dependence is hardly observed in the cutting resistance and the machined surfaces of both specimens. The cutting ratio is in the range of 0.6∼0.7, and the shearing angle shows the values as large as 0.64∼0.58 rad. The highest values of the cutting temperature in pure magnesium and AZ 91 magnesium alloy castings are 573 K and 621 K, respectively, at the cutting speed of 15 m/s. From the above results, it has become clear that a high speed and a heavy cutting can be applied to both specimens. There is no particular problem in the aspect of safe working in the range of the cutting conditions adopted in this experiment.

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  Aluminum alloy specimens cast by vertical pressure diecasting have higher mechanical strength than that in the specimens by conventional pressure diecasting process. In cast specimens produced by vertical pressure diecasting process, which have thick section and machined surface, the lowering of the strength is not serious in comparison with that in the specimens having thin section and as-cast surface. Tensile strength of cast specimens is good correlation with their specific gravity. The coarse primary crystals formed at low casting temperature have an negative influence on the mechanical strength.

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TiやAl等のとCFRPは航空宇宙産業において重要な材料であるが、これらの接合には主として機械的締結が用いられ、応力集中による割れや重量増加などの問題が存在する。そこで、本研究では線形摩擦接合(Linear Friction Welding : LFW)に着目し、シランカップリング処理とLFWを組み合わせることで、とCFRPを直接接合する方法を検討し、継手強度に及ぼすLFW条件の影響について調査した。

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  The cooling rate and solidification time of aluminum die castings were estimated by their dendrite arm spacing (DAS II). DAS II of the die castings is the smallest in their surface layer, increasing toward the center of section thickness. The cooling rate is about 1000°C/s in the surface layer, whereas it is only 20-30°C/s in 2mm inner from the surface. Namely, the aluminum die castings are solidified toward their center at a remakably large temperature gradient. Furthermore, the solidification time of the die castings was estimated to be 1 sec in the surface layer, and 2-6 sec in the center of 3-7mm section thickness. The cooling rate and solidification time are more strongly influenced by shooting conditions rather than the section thickness of the castings.

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  Effects of Mg addition up to 0.4% and solidification time on the crystallizaion of AlFeSi compound in Chinese script form in Al-6%Si alloy castings caused by melt superheating were studied. An effect of melt superheating on the impact strength of AC4C alloy castings containing Fe0.3 to 0.9% was also studied. Three types of AlFeSi compounds with needle-like, indefinite and Chinese script shapes and AlMgFeSi compound with indefinite shape are observed in Al-6%Si-Mg alloy castings. Mg addition inhibits the crystallization of AlFeSi compound in Chinese script form. When solidified within a shorter time, the compound crystallizes at lower superheating temperatures. AlMgFeSi compound is insusceptible in morphology. When superheated at elevated temperatures, the impact strength of AC4C castings except as cast permanent mold castings increases. This is caused by not only crystallization of AIFeSi compound in Chinese script form instead of needle-like and indefinite forms but also size reduction of the needle-like compound even at high Fe content.

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  Molten metal flow behavior during fast shot injection with 500t to 1650t commercial die casting machines was studied in the filling portion of the die cavity in the shape of disc, box and plate.
  The die cavity was filled with a molten metal flowing out of the gate and moving toward the final filling portion as shown in the equal time diagram. The velocity of the molten metal is as high as 15m/s to 20m/s at the gate of die cavity, but it decreases abruptly within a passage of 20cm to 25 cm and reaches 2m/s to 5m/s at the final filling portion. The gas pressure increases from the gate to the final filling portion. The velocity of metal decreases with increase in the gas pressure at the final filling portion. Provision of an appropriate gas vent in the final filling portion increases the velocity of the molten metal, resulting in a few casting defects at this portion of the die castings.
  When molten metal having a temperature of 640°C was poured into the shot sleeve of die casting machine, its temperature lowered rapidly to its solidifying temperature and was injected into a die cavity in a solid-liquid mixture state.

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  The molten metal pressure in a die cavity was measured insitu during casting of an aluminum alloy (JIS ADC 10) in a 90 tonne cold chamber-type diecasting machine. The solidification structures of the as-cast materials were examined by light and scanning electron microscopy techniques. Mechanical properties of ASTM standard diecast specimens were measured by tensile and charpy impact tests. With increase in injection velocity and/or rising in temperature, the solidified microstructure becomes finer, and the measured mechanical properties, especially ductility becomes superior. When the molten metal pressure in the die cavity was below 600kgf/cm², the tensile strength of the diecastings was reduced. Microstructural examination revealed that extensive shrinkage microporosity and a coarse dendritic structure were present in the diecastings cast under lower pressures. The reduced strength of the observed microfeatures is discussed in terms of the observed microfeatures.

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The effect of cold rolling, which set 20% to 40% area reduction along the crack propagation direction, on the Charpy impact properties of a medium strength aluminum alloy (5083) was established by utilizing instrumented Charpy impact tests at temperatures ranging from 77K to 473K for four kinds of specimens which were cut out from a rolled plate in the directions parallel and vertical to the rolling direction. A standard V-notch was formed on the rolled surface of two specimens and in the vertical direction on the remaining two specimens.
In general, by cold rolling the absorbed energy decreased remarkably by about 30 to 60% as compared with that of the unrolled 5083-O specimen in the temperature range of 77K to 373K. It was found that the effect of cold rolling on the absorbed energy differed considerably depending upon the crack propagation direction. When the crack propagation direction was vertical to the rolled surface, an extraordinary increase of absorbed energy up to about 120% appeared at 77K as compared with that of the unrolled specimen. On the other hand, when the crack propagation direction was parallel to the rolled surface, the increase of absorbed energy was about 35 to 55% at 474K.
It is assumed that this extraordinary increase of absorbed energy at 77K is due to the occurrence of laminated fracture which was promoted by cold rolling.

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  A computer system for analyzing the molten metal flow in die cavity of a plate shaped die castings has been developed. The molten metal flow in the die cavity was simulated by solving reformed 2D Navier-Stokes equations considering the thickness of the flow. The apparent kinematic viscosity of the actual flow in the simulation, 2cm²/s which conformed to the actual flow was obtained. With the simulation system using this coefficient, the molten metal flow in the die cavity of the plate shaped die castings having the gas defects was analyzed, enabling the decrease of the defects.

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