Friction welding a 5052 aluminum alloy with different shape was investigated for the welding of a stud to plate. Both solid bar with five different size drilled holes and pipe were used for studs. The rotational plane was observed to move on the welded layer of the joints of stud to plate. Hardness distribution of the friction welded joints of pipe to plate indicated the existence of the softening areas at the heat affected zone of the pipe side. The hardness of the transferred metals of joints was higher than that of the plate, but was lower than that of the pipe. Both the maximum rupture load and elongation of friction welded joints of pipe to plate were lower than those of the base metals. Regardless of the diameter of drilled holes, the maximum rupture loads for all the welded joints were lower than those of the base metals. All the friction welded joints of pipe to plate were fractured at the transferred metals.

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The yield stress of Al-Mg polycrystalline alloys follows the Hall-Petch relation: σ_y=σ_O+K_yd^-1/2, where both the friction stress, σ_O and pinning constant, K_y depend on the quenching temperature and Mg content, C. The relation between σ_O and C can be experimentally expressed as σ_O=0.6με^4/3C, where μ is the shear modulus and ε is the size misfit parameter. This result agrees well with a theory of solid solution hardening. The friction stress σ_O increases as the quenching temperature increases, which can be attributed to the increase in the number of quenched-in vacancies. The fact that the pinning constant K_y decreases as the quenching temperature increases and as the Mg content decreases, can qualitatively be explained by the size of Cottrell atmosphere.

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The emission process of hypereutectic Al-Si alloys were investidated by using both high and low voltage spark discharges. The dependency of Si/Al intensity ratio on the primary Si particle size were studied in the samples of various Si contents and primary Si particle sizes. The emission discharge progressed from eutectic Si and progressed through the surface of primary Si particles, and reached the α-phase and the primary Si particles. In the case of high voltage spark discharge, the Si/Al intensity ratio increased exponentially with the decrease in size of Si particles. It was caused that the specific surface area of primary Si particles increased with the decrease in size of primary Si particles. In the case of low voltage spark discharge, however, changes in the primary Si particle size did not have any significant effect on the Si/Al intensity ratio.

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Superplastic deformation behavior of a Zn-22%Al eutectoid alloy was investigated based on the changes in m values and true strain rate during the tensile deformation. Transition from the uniform elongation to the neck formation stage was changed by changing the initial strain rate taking account of the maximum m value against the true strain rate. Preliminary estimation of the fracture elongation was also given from the initial strain rate. Transition from the uniform elongation to the necking stage could be predicted from the differentiation of the m values with regard to the true strain rate during the tensiles uperplasticd eformation. Fracture elongation changed in accordance with the distribution of the true strain rate and m values. The wide distribution of high m value resulted in the increased fracture elongation. The elongationo btained in the first superplastic deformation stage (uniform deformation) was estimated using the experimentally proposed equation based on the initial strain rate.

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Cast samples having different copper concentrations were remelted and then were kept at fixed temperatures varying from 10 to 200K above the liquidus temperature of Al-Cu alloys phase diagram. The primary α aluminum dendrites appeared both just below the net, and at the top of ingot, when hypoeutectic alloys containing 31 to 33mass% Cu were solidified in a graphite mold in which a stainless steel net was set horizontally. On the other hand, the primary CuAl₂ in the hypereutectic alloys containing 34 and 35mass%Cu appeared on the net and at the bottom of ingot. The primary α aluminum dendrites were less dense than eutectic liquid and floated in the melt after crystallization, and primary CuAl₂ crystals sedimented in the liquid because they were denser than the eutectic liquid. The variation of holding temperatures and the duration of time in the molten state had no effect on the gravity segregation of those ingots, since no temperature gradient existed in the liquid and no thermal diffusion occurred under those conditions. Gravity segregation in Al-Cu alloys containing various copper concentrations was caused by floatation or segregation of primary crystals in the melt during solidification.

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Wetting of hot-pressed β-SiC by liquid aluminum was studied by sessile drop method under 1×10⁵Pa in He-3vol% H₂ and in a vacuum of 1×10^-3Pa. The contact angle (θ) varies during holding at constant temperature. In the wetting in He-H₂, four stages are observed: (I) decrease in θ immediately after dropping, (II) Initial stational wetting with constant θ, (III) spreading of aluminum on SiC substrate with decrease in θ and (IV) stational wetting with constant θ. When the interfacial reaction occurs between SiC and the drop, two interfacial energies, γ_LV and γ_SL decrease, and hence θ decreases at the stage III. In the wetting in a vacuum, three stages are observed: (I') initial stational wetting, (II') decrement of θ, and (III') stational wetting. The reaction occurrs at the stage I', while the decrement of θ at the stage II', is caused by evaporation of aluminum. θ decreases with increasing temperature, and a significantly abrupt decrement of θ is found at a certain temperature in each atmosphere. This phenomenon is caused by the interfacial reaction between SiC and aluminum. In particular, this temperature in a vacuum is lower than that in He-H₂ due to evaporation of aluminum.

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The relation between microstructures and mechanical properties has been investigated on Al-8%Fe and Al-8%Fe-1-3%Zr alloys produced by the combined rapid solidification and extrusion processing. All extrudates exhibited deformation structures produced during extrusion at 703K. Dislocation structures were stable even after exposure at 573K for 100 h. At temperatures higher than 573K, softening took place in all specimens due both to the recovery of dislocation structures and to the transformation of the metastable Al₆Fe phase to the coarse and stable Al₃Fe phase. Zirconium remained supersaturated in the aluminum matrix even after extrusion. Tensile property of Al-8%Fe alloy markedly increased with increasing amount of zirconium up to 623K. This effect of zirconium was explained by the increased supersaturation of zirconium in the matrix.

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Micro-structural change in 1100, 3004, 5052 and 5082 aliminum alloys due to single pass rolling at temperature betwean 50°C and 350°C has been investigated. Dynamic recovery during rolling was influenced by both rolling temperature and Mg content. In the alloys containing Mg, finer subgrain size and existence of dislocations in subgrains were found, though no subgrain formation were observed in 5052 and 5082 alloys at lower rolling temperature, due to inhibited migration of dislocations. After rolling, hardness decreased due to the static recovery, while recrystallization occured at elevated temperature. In the alloys containing Mg, the recrystallization was accelerated by high density of dislocations which were introduced during rolling.

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