Plastic fractures of age-hardened aluminum alloys (Al-Cu, Al-Cu-Mg, Al-Mg₂Si, and Al-Zn-Mg) were investigated by tensile test and electron fractography. The following results were obtained.
(1) True fracture stresses in Al-Cu, Al-Cu-Mg, and AlMg₂Si alloys increased with the progress of agehardening, but violently decreased in the fully hardened state; while, in Al-Zn-Mg alloy, the stress scarcely changed with the progress of age-hardening and also decreased in the fully hardened state.
(2) By the analysis of fractured surface by electron microscopy, the fractures of super-saturated solid solution were characterized by large and uniform dimples. However, in age-hardened alloys, the fractured surfaces exhibited an extremely wide range of the dimple sizes. As to the topographic features of the surfaces, serpentine glide was observed in Al-Mg₂Si and Al-Zn-Mg alloys more than in Al-Cu and Al-Cu-Mg alloys. The second phase particles and inclusions distributed in the alloys played an important role in the plastic fracture, but they were not further investigated.
(3) Intergranular fracture increased with the progress of age-hardening in any alloys, but it very often occurred in slightly aged specimens of Al-Zn-Mg alloys. There are two contradictious theories against the role of precipitate-free zones along the grain boundaries in the fracture process of these alloys. It was confirmed by fracture topography that plastic fracture tended to occur in the vicinity of the grain boundaries, but the role of precipitate-free zones in the plastic fracture is not yet cleared.

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Behavior of G. P. zones in aluminum alloys during the early stage of fatigue has been studied by electrical measurement. In room-temperature aged high purity Al-1.5wt.% Mg₂Si alloys, the electrical resistivity decreased with cyclic deformation. During the subsequent natural ageing, the changes in the resistivity took place in three stages, which were in quite the same way as the changes in 6061 alloys previously reported. The 1st stage was a slight decrease of resistivity which may be due to the anne ling out of excessive vacancies generated during the cyclic deformation. The 2nd stage was rapid increase of resistivity due to the reformation of G. P. zones. The 3rd stage was a gradual increase of resistivity due to the growth of G. P. zones. Similar results were given by repetition of cyclic deformation and natural ageing. Accordingly, it was concluded that the reversion of G. P. zones happened under the cyclic loading, but the reformation of the zones happened after the unloading.
In Al-2.0% Mg alloys aged at room temperature, the process of resistivity change was the same as that in high purity Al-1.5% Mg₂Si alloys. In Al-3.0% Cu and Al-3.0% Cu-0.4% Mg alloys aged at 130°C for 2hr., the changes in resistivity during the subsequent natural ageing took place in three stages apparently different from those in Al-Mg₂Si alloys. The resistivity increased in the 1st and decreased in the 2nd; but did not change in the 3rd stage, It was concluded by kinetic analysis that the reversion of G. P. zones took place under the cyclic deformation; the reformation of the zones during the natural ageing in Al-3.0% Cu and Al-3.0% Cu-0.4% Mg alloys also took place under the cyclic deformation

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Aluminum is a light metal having high corrosion resistance in the atmosphere and in many kinds of artificial waters.
Aluminum is very active, but becomes passive when exposed to water.
The author studied pit formation on 1S sheet in pure water and many kinds of artificial waters. The corrosion behavior of aluminum in pure water was observed sensitive to a small amount of impurities or intermetallic compound α (FeSi) contained in the metal.
A pit in such a case was formed in the zone of aluminum surrounding the compoundα (FeSi) which was catholic against aluminum.
When the degree of pit formation in pure water was taken as a standard, the effects of adding reagents to pure water were summarized as follows.
(1) Neutral or acid salts (NaCl or MgCl₂ 1-5ppm) were not effective for pit formation.
(2) Alkaline salts (Na₃PO₄ or Na₂SiO₃ 1-5ppm) inhibitted the pit formation. However, general corrosion occurred for Na₂SiO₃ of 10ppm.
(3) Alkaline salt (Na₂CO₃ 3-5ppm) accelerated the pit formation.
(4) In any artificial waters, no macropitting was observed.

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Copper concentrate-ores were generally filled in jute bags for transportation by ships and trains from Peko Mines Co., Australia to Sumitomo Metal Mining Co., Japan. The rationalization of shipping works for the ores was required, because there were dangers of ignition of accumulated bags due to heat generation of the filling ores when they were moistened and exposed to high atmospheric temperature.
In February 1967, the "Spensa-maru" which had been built for exclusive transportation of copper, zinc, and lead ores, was put in commission. The ship solved the above problems by the application of palletization for avoiding the heat generation and ignition and also getting rationalization of shipping work.
In designing the pallets, there were no other proper means than assuming uniform distribution of the load on the pallets. However, the practical distribution of the load was not always uniform. Sometimes, the stresses in frames are higher than those of calculated values; or deformation of lower deck-board of second floor pallet is caused by concentrated load due to rugged arrangement of jute bags. However, these stresses or deformation shall be neglected in the practical work, if they are small.
As being understood from the above facts, the loading test must be conducted with the practical loads.
Of course, special care shall be taken in the operation of fork-lift trucks, and the pallets must be equipped with replaceable parts against damages by accidents.

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