Although JIS AC5A aluminium casting alloy has long been used, it is still not perfectly defined how its physical and mechanical properties are affected by the contents of components within the specified ranges, casting and heat-treatment conditions.
This is to report on the study for defining the above points and the findings are summed up as follows:
(1) Mg contained within the specified range does not affect much on its properties, while the higher Cu content increases the tensile strength at high temperature and the addition of about 0.1% of Ti improves its properties to some extent. However, the lower Ni content is desired even within the specified range, because it works to reduce the proof stress.
(2) Its properties are not particularly affected by the casting temperature. It is easy to use because not strict control of casting conditions is required. But, to obtain better properties, the mould temperature must be kept lower. The casting cavity appeared in the products of this alloy is quite small. It should be noted, however, thermal expansion is lower and wear resistance is higher as compared with JIS ACBA and AC8B aluminium alloys.

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This report referres to the experiment for investigating the changes in grain size of primary Si, specific gravity and Brinell hardness of Al-Si alloy (20% Si) cast with permanent mould, when the alloy is treated by use of polytetrafluoroethylene.
The findings are summed up as follows:
1) In case the polytetrafluoroethylene is added, the primary Si crystals in the alloy are remarkably refined. This reaction is more promoted when very small amount of phosphorus is added together with polytetrafluoroethylene.
2) The most effective amount of polytetrafluoroethylene is 0.05-0.075% with 0.001% of phosphorus.
3) Specific gravity of the alloy are 2.62-2.64.
4) Brinell hardness of the alloy is higher than that of the same alloy sand-cast.

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The endurance properties of aluminized specimens were investigated by the Schenck's "plane bending fatigue machine." This is to report on the fatigue crack of the aluminized steel. The findings from the above experiment are summed up as follows:
(1) The fatigue cracks are at first seen at the boundary between aluminium layer and aluminium-iron layer and then rapidly developed toward the base steel.
(2) Most of the cracks which have passed into the aluminium-iron layer go into the base steel through mountain-peaks.
(3) The appearance of the cracks is easier to find in the case of thicker aluminium-iron layer.
(4) The iron-aluminium layer develops the vertical fatigue cracks but not the horizontal ones.
(5) A crack which grows at the first stage is not always to be the cause of the fatigue cracks.

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For the purpose of observing microstructural change in cold rolled (at 20°C) titanium plate at higher temperature under the vacuum of 10^-5mm Hg, observation has been made using high temperature microscope.
The results obtained are as follows:
1) At the temperature of recrystallization and grain growth determined through the tensile test and microstructual observation on cold worked and annealed titanium plate, structural change has been observed under high temperature microscope which occured from the region of high deformation strain within grains.
2) Recrystallization temperature has been determined to be between 460° and 580°C, where structural change has been observed by high temperature microscope as well as changes in tensile properties in cold worked and annealed titanium plate after heating.
3) Makings observed within grains after cold work has been found to disappear at the high temperature of say 700°C where grain growth is observed.
4) Heavily etched α boundary has been found to be retained after α→β transformation point was exceeded, but new β phase region has begun to be observed.
5) Small amount of oxygen has been introduced into the polished but unetched specimen surface at 500°C upon heating. No microstructural change, however, has been observed.

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