To compare the thixoformability between granular crystal structures and dendrite crystal ones of 6070 and 7075 aluminum alloy billets produced by the semisolid and conventional DC continuous casting, the thixoforming test was performed at a constant deformation speed of 4mm/s in an argon atmosphere. The test piece consisting of granular crystals of 6070 alloy reveals that the thixoforming power was less than 1 kN during three quarters of forming process and the maximum power at the final stage was 18kN. In contrast, the test piece consisting of dendrite crystal structure reveals that the power was more than 5 kN at the first stage and as the forming process proceeded, the power increased. The maximum power at the last stage was 35 kN. Granular grains of primary α aluminum coexisting with the liquid phase were possible to move easily into the die cavity, because the liquid phase played an important role of lubricant as the thixoforming was performed to the semisolid slurry. However, when dendrite network was developed throughout the billet, the liquid phase among interdendrites only moved at the first stage. Hence, the deformation resistance increased and the thixoforming power became larger at the later stages. The same results were obtained by the thixoforming of 7075 aluminum alloy.

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A polarization measurements of 99.999% purity aluminum specimens in acid, neutral and alkaline solutions in which they are chemically and electrochemically pretreated, have been made to clarify the difference of electrochemical behavior between in general dissolution range and in pitting attack occurrence range. It is discussed that the reaction of general dissolution corresponds to that of metallic aluminum to aluminum hydroxide and the reaction of pitting attack corresponds to that the metallic aluminum combines with chloride ions to form aluminum chloride compounds such as AlCl²⁺ and AlCl₂⁺.

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The measurements of contact angle between molten aluminum and MgAl₂O₄ spinel substrate and surface tension of molten aluminum, and the direct observation of aluminum surface were conducted. An oxide layer, which was formed in the whole surface of molten aluminum during elevating temperature, disappeared almost within about 2 ks at 1273 K. It is guessed that the layer consists of spinel oxide. An increase of surface tension and a decrease of contact angle were caused by elimination of the oxide layer. The marangoni flow, which probably resulted from the difference of surface tension, was observed from upper to lower part of aluminum surface.

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The mechanical alloying process of Al–B system mixed powders under a surging mode of a high energy planetary ball mill was investigated by means of microscopic observation, X-ray diffraction and hardness measurement. In the X-ray diffraction pattern, each Al peak shifted to high angle side with increasing the milling time. These peak shifts correspond to decrease in the lattice parameter of Al. The supersaturated solute B atoms take the substitutional positions in fcc Al cluster and resulted in lattice construction of α–Al. B atoms about 13 atomic percent solubled in the solid Al during mechanical alloying of Al–B mixed powders. The average grain size of Al–30at%B mixed powders milled for 345.6 ks was about 15nm. For the reason of solid solution hardening by B solubilities to solid Al, grain refinement of α–Al phase and work hardening during mechanical alloying, maximum hardness of Al–20at%B and Al–30at%B mixed powders was more than 400 HV.

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