In this study, solidifications of aluminum-silicon binary alloys in step molds and simple shaped cylindrical molds were investigated on alloys of containing 6.6, 11.6, and 20.0% of silicon.
The process of solidification of these alloys consisted of four stages; liquid, solid solution, eutectic, and solid. Cooling velocity of Al-20.0% Si alloy was higher than that of Al-6.6% Si alloy in the pro-eutectic solidification temperature range in which slikd and liquid phases co-existed. Then, it would be suggested that the latent heat of hypo-eutectic alloy generated on the solidification of primary crystals was greater than that of hyper-eutectic alloys. The solid phase of silicon primary crystals, which had been formed before eutectic solidification, diminished the radiation of heat to the outside. Consequently, the period of eutectic solidification of Al-20.0% Si alloy was longer than those of other aluminum-silicon alloys used in this study.
The time of solidification period of a simple shaped cylindrical casting was proportional to the value of (volume/suface area)² as far as the latter value was less than 0.3, when it was cast in a given shell mold.
The ratio of (volume of shell mold/volume of casting) will be an important factor indicating the cast structure, because the structure is more fine-grained with the increase of that value.

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This paper describes the effects of addition of Zr or Ti+B on weld cracking and cast cracking of Al-Zn-Mg alloys.
The suseptibility to hot cracking was evaluated by Fisco type weld cracking test, I type weld cracking test and ring cast cracking test.
The results obtained were as follows.
(1) The addition of Zr or Ti+B to base or filler alloy had remarkable effects on reducing the susceptibility to hot cracking of Al-Zn-Mg alloys
(2) Among the factors controlling weld cracking, the grain size of weld metal was remarkably affected by the addition of Ti+B. The size was markedly refined by its addition and stable refining was still maintained after remelting. Then, the mechanism of preventing hot cracking by Ti+B addition would primarily be caused by the refining of grain size.
(3) The addition of Zr had great effects on shapes and distribution of low melting compounds or eutectic the grain boundary at nearly the end of solidification. The dihedral angle was greatly increased with the addition of Zr. Then, the mechanism of preventing cracks by Zr addition would primarily be caused by the effects on shapes and distribution of liquid composed of low melting compounds and eutectic

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As described in the previous report, it was found that silumin has a considerably high cutting resistance which gives fairly great wear of tools; and good cutting finish surface cannot easily be obtained. It was also found that improvement of its machinability was considerably effective by the addition of small amounts of sodium, calcium, etc., but was not effected by the addition of phosphorus.
In this paper, there are examined the effects of addition of various amounts of sodium and calcium on machinability with respect to cutting resistance, tool life, cutting temperature, surface roughness, and chip treatment.
As the results. it was found by the experiments that the machinability of silumin was effectively improved by the addition of 0.0280.04% of sodium or 0.180.52% of calcium. By the addition of a small amount of sodium, the mechanical properties were improved with its increasing content. However, cutting resistance was decreased, but tool wear and surface roughness were increased, and chips gradually flowed in continuous coiled form with increasing sodium amount. The addition of a small amount of calcium had no great effect on mechanical properties, but was effective in improving machinability; such as slight decrease in cutting resistance and drop of cutting temperature with its increasing content as well as extension of tool life and improvement of surface roughness finished.

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The liquidus line of K₃AlF₆-MgF₂ system was determined by differential thermal analysis. The melting point of K₃AlF₆-MgF₂ system was lowered with the increase of MgF₂ and reached the minimum of 930°C at 42.5 mol% of MgF₂. It was gradually raised with the further increase of MgF₂ and reached the maximum of about 1, 027°C at 6070 mol% of MgF₂. Then, it was again lowerd with the further more increase of MgF₂.
Reversible reaction of K₃AlF₆ + 2MgF₂_??_2KMgF₃ + KAlF₆ was observed by X-ray analysis of the solidified bath. The equilibrium constant of the reaction was discussed.
Heat of fusion of alkali cryolites was calculated from the measured values by cryoscopic method. The values of heat of fusion of LiAlF₆, Na₃AlF₆, and Li₃AlF₆ were 20.7, 27.4, and 27.6 kcal/mol, respectively.

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The role of the dispersed second phases in the abnormal grain growth of 5056 alloy plates is discussed in this paper.
The counting of number of particles by microscopy, electric resistivity test, and measurement of lattice parameters were made on the following two series of alloys.
Series C: Al-5% Mg alloys containing small amounts of Mn and/or Cr, which were obtained by direct cold rolling of the casting.
Series D: Al-5% Mg-Mn and/or Cr alloys containing small amounts of Si and Fe, which were obtained by hot rolling and successive cold rolling of the casting.
The results obtained were as follows:
(1) The abnormal grain growth in 5056 alloy was due to the secondary recrystallization which had been caused by the precipitation and dissolution of fine particles containing Mn and/or Cr.
(2) In the alloy having the composition of commercial grade, which had been prepared by further addition of Si and Fe, the abnormal grain growth was slightly accelerated, in particular, in ultimate grain sizes.
(3) This phenomenon, abnormal grain growth, took place in the following both cases: one was in direct cold rolling of the casting, and the other was in indirect cold rolling, of cold rolling after hot rolling.
(4) Three stages of precipitation according to annealing temperature were observed in this study. The 1st stage, having peak at 200°C, appeared in all the alloys and it would be β-phase in Al-Mg binary system. The 2nd stage, having peak at 350°C, appeared in the alloys containing Mn and/or Cr and it was significant in the present study of the abnormal grain growth. The 3rd stage, having peak at above 550°C, appeared in the alloys containing Cr, and the grain growth was effectively inhibited in this stage.

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