The impurity diffusion coefficients of Cu in Al over the temperature range between 667 and 930K were determined by the serial sectioning method using the radioisotope ⁶⁷Cu. A slight curvature was observed in the Arrhenius plot of the impurity diffusion coefficients near the melting point of Al. The isotope effect factor for the impurity diffusion of Cu in Al was determined in the temperature range between 694 and 926K, using three isotopes ⁶¹Cu, ⁶⁴Cu and ⁶⁷Cu. The isotope effect factor for the combination of ⁶¹Cu with ⁶⁷Cu are found to be different from that of ⁶⁴Cu with ⁶⁷Cu. The isotope effct factor decreases with the increasing temperature in a range near the melting point of Al. These results were discussed on the basis of the contribution from divacancy to the impurity diffusion of Cu in Al near the melting point of Al.

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Rapidly solidified flakes of Al-9%Zn-2.5%Mg-1%Cu alloys containing Co, Fe, Mn and Fe+Ni were produced by atomizing the alloy melt and subsequent splat quenching onto a water-cooled copper single roll. Consolidation of the flakes was done by cold pressing, vacuum degassing and hot extrusion at a reduction ratio of 25 to 1. Fine and uniform dispersion of transition metal compounds was attained in all P/M materials, and Mn bearing alloy showed the highest hardness whereas Co bearinig one the lowest. The age hardening behavior was not affected by the addition of various transition meals, and hence Mn bearing alloy showed the highest peak hardness. Tensile strength of T6 treated Mn beariing P/M alloy was 817MPa with 6wt% Mn addition, and 787MPa with 2wt% Mn. In T6 treated P/M Mn bearing alloys, an elastic modulus higher than 82GPa, a specific elastic modulus higher than 28GPa and a specific tensile strength higher than 270MPa were obtained. These values are even higher than those of Ti-6Al-4V at room temperature.

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The effect of pre-heat treatment on the superplastic behavior of 7475 aluminum alloy has been investigated with special reference to the role of precipitates which are introduced during heat treatment. Particles which precipitate either during quenching after solutionizing treatment or during annealing for straightening sheets (below 633K) have no effect on the superplastic properties because they can easily be solved into the matrix when heated to high temperatures. In contrast, particles which have coarsen during long term heating at 673 to 713K accelerate the cavitation and hence degrade the superplastic ductility.

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A method of superplastic forming with pre-straining is developed on the basis of the study on the effects of excess solute atoms before cold rolling and the reduction of cold rolling in thermomechanical treatment on superplasticity. The quenched and cold-rolled sheet with and without pre-straining at an intermediate temperature showed, respectively, the elongation of 900% and 100% in tensile test at 773K and 2.7×10^-3s^-1. This result indicates that the excess solute atoms are required before cold rolling in order to obtain an excellent superplasticity at high strain rate. The temperature of pre-straining decreased with increasing reduction of cold rolling and was lower than that of recrystallization determined by DSC. Stable subgrain structure is obtained during pre-straining at the above mentioned temperature because excess solute atoms precipitate on the dislocations and retard the recovery of substructures. The excellent superplasticity can be attributed to the substructure consisting of fine grains less than 10μm.

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The sponge cast taluminums with mean pore size of 7, 13 and 20μm in diameter were produced by the process, i.e., pressure casting of molten aluminum into the NaCl particulate preform and then dissolving away the NaCl skeleton from the NaCl-aluminum composite. The study was undertaken to ascertain the feasibility of the sponge cast aluminum to apply to the slip casting mold for zirconia ceramics. Slip casting by using the sponge cast aluminum with 7μm pores could be carried out in the same way as slip casting by a conventional plaster mold. In the case of the sponge cast aluminum mold with larger pores, demolding of green was difficult without plaster coating on the mold surface, and the greens were soft as compared with those by the plaster mold. Differences of bulk density and bending strength between the specimens obtained by the sponge cast aluminum molds and those by plaster molds were not detected.

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Metthiessen's Rule (M.R.) and empirical relations between resistance ratio (R=ρ₃₀₀/ρ₇₇) and resistivity (ρ₇₇) of Al-Fe and Al-Si binary alloys containing total other impurities less than 0.1% were investigated. Relations corrected for binary solid solutions having deviation from the M.R. were proposed. To avoid systematic positive error of geometrical size factor, size fac-tor was determined by density method. Though there remains a possibility of correction in future because of effects of the other impurities, the empirical relations for the Al-Fe dilute alloys,
2.5<ρ₇₇/nΩ•m=24.767/(R-1)+0.0574<3.5
and for Al-0.37-1.35%Si alloys,
5<ρ₇₇/nΩ•m=25.854/(R-1)-0.1487<11
were temporarily recommended. Gradient of ρ₇₇ vs. (R-1)^-1 plot for the Al-Fe alloy was smaller, and that for the Al-Si alloy was larger than ideal value, suggesting "negative" and "positive" deviation from the M.R., respectively. On the comparison of these relations, the previous relation reported for the commercially pure aluminium coincided to those of binary alloys within 1% accuracy.

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Cyclic bending fatigue tests were performed on alumina short fiber reinforced AC8A aluminum alloys in order to examine the effects of volume fraction of fibers and nonfibrous inclusions (shots) on S-N curves. Fatigue limit stress increased with increasing volume fraction of fibers. The effect of shots on S-N curves was very little when shot content was less than 0.1%. Cyclic fatigue crack propagation rate was also measured on the composites. The crack propagation rate increased with increasing volume fraction of fibers when it was compared at the same stress intensity range.

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