Cylindrical specimens of Al-20%Si alloys containing primary silicon crystals of different sizes were prepared and their thermal shock behavior was examined. The specimens were quenched into iced water after heated at 550°C for 20 min., and this was repeated. After thermal shock cycles, macroscopic and microscopic examinations were made and the resistance to thermal shock was discussed in relation to the size of primary silicon crystals.
1) No crack was observed on the surface of the specimens with refined primary silicon crystals after subjected to the thermal shocks for 400 times. However, some cracks were detected in the central part after about 100 cycles.
2) Cracks initiated at the interface between primary silicon and α-aluminum and propagated into the silicon crystal.
3) Thermal shock cycles resulted in the deformation of the specimens, but it was confirmed that the resistance to deformation was higher in the specimens with refined primary silicon crystals.
4) With an increase in thermal shock cycles, needle-like eutectic silicon changed its shape to spheres, but little change was observed for primary silicon crystals.

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Compressive tests were performed on an eutectoid Al-Zn alloy (A2) and an extruded Al-Zn-Cu-Mg eutectoid alloy (A4) at temperatures between 100°C and 250°C and microstructural observation was made. Creep tests at room temperature were also carried out. Compressive stress of A4 was about 2 or 3 times higher than that of A2 at a constant strain rate and temperature, and this tendency was predominant at low temperatures. The strain rate sensitivity index, m, for A4 was greater than 0.3 at temperatures above 180°C, and this alloy was deformed superplastically. Therfore, it seems that the influence of additions of Cu and Mg on superplastic behavior is insignificant at high temperatures. The activation energy of A4 and A2 was equal to 2.3 eV and 1.2 eV, respectively, the latter value for A2 corresponded to the activation energy of volume self diffusion of Zn. A principal mode of deformation in the superplastic region for A4 and A2 was grain boundary sliding. A creep test at 10°C showed that the creep resistance of A4 was much higher than that of A2. Consequently, it becomes evident that some additions of Cu and Mg will enhance the practical use of the Al-Zn eutectoid alloys.

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It is well known that a small addition of Sn, Cd or In to an Al-Cu alloy slows down the aging rate at low temperature but accelerates it at higher aging temperature. However, this mechanism seems to be still unknown, although the isothermal aging process in these alloys has been discussed in terms of the proposed models. In the present paper, we shall describe the experimental results on the effects of the amount of ternary addition on the aging process at low (0°C) and high (about 100 to 190°C) temperatures in Al-Cu alloys containing small amounts of Sn, Cd or In. Measurements of hardness, heat capacity and electrical resistivity, X-ray diffraction analysis and transmission electron microscopic observation were carried out. The results obtained are as follows.
(1) The aging process at low temperature in Al-Cu-Sn ternary alloys with 2 and 4 wt%Cu containing 0 to 0.2 wt%Sn were suppressed with increasing excess Sn above the solid solubility of Sn in α-phase of ternary alloys at the solutionizing temperature.
(2) The experimental results showed that the age-hardening rate at high temperature in these alloys were accelerated in comparison with the binary alloys, and this effect was more pronounced with increasing excess Sn.
(3) Electron microscopic observation revealed that θ' precipitates were finer and more densely distributed in Al-Cu-Sn alloys.
(4) Small dark spots were found in an Al-4%Cu-0.1%Sn alloy aged at 190°C for 20 min, but they were not observed in the binary alloy.
(4) Among the three additional elements, the effect on the aing rate decreases in the order; Sn>In>Cd.

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Rolled sheets were prepared for two Al-Mg₂Si monovariant eutectic alloys; alloy E of the Al-Mg₂Si quasibinary eutectic composition and alloy M containing excess Mg, and their metallography, annealing behaviors, age hardening and tensile properties were examined.
The completely annealed specimens showed relatively high strength due to the presence of fine dispersion of Mg₂Si particles. The Al matrix of alloy E were found to be age-hardened, whereas that of alloy M showed no age hardening at all. This marked difference in the Al matrix of the two alloys is considered to be caused by a rapid decrease of the maximum solid solubility of Mg₂Si in Al with increasing the amount of excess Mg. The tensile strength at room temperature was about 33 kg/mm² in both alloys. The specimen of non-heat treatable alloy M showed thermally more stable strength at 150-250°C. Taking excellent hot workability into account, Al-Mg₂Si monovariant eutectic alloys were concluded to have a possibility of practical application as wrought aluminum alloys.

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The modulns of longitudinal elasticity and their temperature dependence in commercial aluminum cast alloys were measured in the temperature range from room temperature (20°C) to 250°C by the resonant frequency method. The results obtained are as follows:
The modulus of longitudinal elasticity tended to decrease weakly and linearly (the tangent of its decrease, m = (-2.4--3.3) × 10²kg/cm²/°C) with the rise of temperature. Within the range of the experiments, aluminum cast alloys were divided into 3 groups, the lst group materials having large moduli of elasticity E₀ at room temperature (i. e., E₀ = (7.15-7.25) × 10⁵kg/cm²) were AC2A-T6, AC3A-F, AC4A-F, AC4A-T4, AC4B-F, AC4B-T4, AC8A-F, AC8A-T4, etc., the 2nd group materials having intermediate moduli (i. e., E₀ = (6.85-6.98) × 10⁵kg/cm²) were AC4C-F, AC4C-T5, AC4C-T6, AC4D-F, AC4D-T6, AC7A-F, etc. and the 3rd group materials showing considerably smaller moduli (i. e., E₀ = (6.58-6.65) × 10⁵kg/cm²) were AC1A-F, AC1A-T6, AC2A-F, etc. However, there were some differences between the moduli in this experiments and the moduli in the other data books, and these were considered due to the difference of the measurement principles and of hypotheses or assumptions involved in these principles, so it is suggested that the moduli of elasticity should be reported with indication of the measuring method.

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