Grain refining effects of TiB₂ dispersed alloys on aluminum were investigated. The TiB₂ dispersed alloys were synthesized by the reaction between titanium and AlB₂, and were added to molten aluminum at 1273 K as the grain refining agents. Excess amount of titanium or aluminum was added to starting materials of the reaction for the purpose of controlling the adiabatic temperatures. In this paper, (1) distribution of TiB₂ particles in molten aluminum, (2) effects of TiB₂ distribution on the grain size and (3) mechanical properties of grain-refined aluminum are mainly dealt with. Since aluminum oxide forms at the inter-particle regions of TiB₂, the dispersion of TiB₂ particles in molten aluminum is not homogeneous when aluminum was added in the starting materials. The excess titanium addition as a diluent, however, improves the distribution of TiB₂ particles. The average grain size of aluminum alloy is effectively reduced by adding the TiB₂ dispersed alloy. The grain refining effects are saturated by about 0.4 vol% addition of TiB₂ particles. The 0.2% proof stress of Al–2 mass%Mg alloy is improved by the grain refining.

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Eleven kinds of aluminum-base composites containing SiC, K₂O·6TiO₂, 9Al₂O₃·2B₂O₃ or Al₂O₃ whiskers were prepared using the liquid metal forging process and their thermal conductivities were determined by the laser-flash method at room temperature. Anisotropic features in thermal conductivity have been detected: samples in which the axes of dispersed whiskers are oriented, exhibit smaller conductivities in a perpendicular direction than in parallel one. The estimations of thermal conductivities were made using the equivalent inclusion method as well as Maxwell and Landau equations and compared with experimental data.

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Extruded aluminum alloy sections are advanced materials in use as lightweight structural members. A secondly forming process such as bending is required when these materials are used for structural members of automobiles. It is known that undesirable deformations as wrinkling and split tend to occur easily when some sections having light gauge are formed by the bending process. This report shows the working limit for the draw bending process of square tubes with a laminated elastic mandrel. A6063S and A6061S square tubes having various thickness are applied to this experiment. It is shown that applying laminated elastic mandrels to this draw bending process is very effective in preventing either primary distortion or wrinkling of compression flange and compressive region of webs. In consequence, higher working limit is obtained by this method. On the working conditions of the thickness ratio t₀/H₀=0.075 or 0.05 of A6063S–O and A6061S–O, the working degree R₀/H₀ reaches to 2.4 or 4.3 without any defects, where t₀ and H₀ mean thickness and the height of the tube respectively.

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In order to improve the quality of aluminum and aluminum alloy billets for use in plastic forming, a new vertical semi-continuous casting process has been devised, using a heat insulating mold. In this study, an attempt is performed to clarify the effects of position of solidification interface in the mold on the surface condition of billets at various casting rates in this process. The lower casting rates show the surface condition with scratches and cracks, and the higher rates show a very rough surface, while the inbetween rates show a very smooth surface. The position of solidification interface in the mold could be examined by use of Sn addition and steel wire depth methods. At a moderate casting rate the solidifying surface of billets emerges at the lower end of the mold and solidification then occurres under the condition of no contact of the solidified surface with the mold surface. Consequently the billets with very smooth surfaces are obtained at the specific casting rate.

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Friction welding of A6061 aluminum alloy to SUS304 stainless steel was conducted. The joint efficiency was estimated from tensile strength, bending strength and torsional strength. The results are as follows, (1) The softened area of A6061 in joints welded at high forge pressures was narrow compared with the joint welded at low forge pressure, because the softened area was expelled into the color under the action of forge pressure. The joint strength depends on the width of the softened A6061 area. (2) Tensile strength of smoothed and notched specimens increased with forge pressure. Maximum joint efficiencies of these joints were about 87% and 93%, and fracture of the smooth and notched specimen showing the maximum efficiencies occurred in the softened A6061 area and at the weld interface,respectively. (3) Bending strength of joints welded at forge pressures not less than 80 MPa was almost saturated and maximum joint efficiency obtained was about 30%. (4) Torsional strength increased with forge pressure. The maximum joint efficiency obtained was about 75%, and joints with the maximum efficiency fractured in the softened A6061 area.

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