Wall thickness of AC4B square column castings was varied by changing a core, size of the castings and then dependence of the solidification time, mechanical strength and dendrite arm spacing (D.A.S) upon the wall thickness was examined. The mechanical strength and D.A.S are also found to be proportional to the n th power of V/S and the values of the exponents were experimentally determined. The experimental results thus obtained agreed fairly well with that obtained from AC4B aluminum alloy cylindrical castings.

抄録全体を表示

In order to obtain a superior thixotropic property even in a high strength 7075 aluminum alloy, a billet with a non-dendritic fine-globular structure has been tried to produce by combining a simple mechanical stirring with the vertical semi-continuous casting process. The trials were carried out under the various stirring conditions; the position of a stirring rotor from the bottom of a mold, the shape of a rotor, the volume of a stirring chamber and the stirring rate. When the temperature within the stirring chamber was nearly constant just below the liquidus temperature and dropped drastically near the liquid-solid interface at the certain stirring conditions, a long sound billet with relatively good surface condition could be produced up to the limitation of the descending capacity of the casting machine. The billet had not only a uniformly fine-grained structure of the average grain size of about 30 μm, but also little macroscopic segregation of the solute elements along the radius in the transverse sections at the various positions along the longitudinal direction of the billet.

抄録全体を表示

We studied the influence of surface coating lubricity on pre-coated aluminum fin stock formability using evaporative lubricants, which was widely used. We controlled the surface friction of pre-coated aluminum fin stocks from 0.05 to 0.8 by the lubricant layer with water-soluble resin coated on hydrophilic layer with alkaline silicate and poly acrylic acid. On the continuous piercing test, according as the surface friction of pre-coated aluminum fin stock was decreased, the wear of piercing tool was decreased and was protected increase of piercing edge R. In case of drowless type forming used bigger piercing edge R, the collar cracking of fins was increased. Therefore, we consider that it has effect of decreasing the collar cracking to decrease the surface friction. On the continuous shearing test, according as the surface friction of that was decreased, the wear of shearing tool was decreased, so that the shearing burr height was depressed. Moreover, in the process of expanding copper tube, according as the surface friction of that was decreased, ‘avec’ phenomenon (fin-pitch disorder of the finned coil) was decreased.

抄録全体を表示

Titanium-flakes-reinforced aluminum-matrix composites with three kinds of titanium volume fractions were fabricated by cold pressure welding of alternately multilayered pure aluminum and titanium foils. Effects of the initial specimen shape of the stacked foils on the shape and size of composites fabricated, morphology of dispersed titanium flakes, and anisotropy of the bending strength of the composites were investigated. Results obtained are as follows: (1) After cold pressure welding, increment in length of the shorter side of the initial specimen increases with ratio of length of the both sides, and increment in length of the longer side decreases with the ratio. (2) The length to width ratio of dispersed titanium flakes in the aluminum matrix increases with increasing ratio of long side length to short side one of the initial specimen. (3) Bending strength in the longitudinal and transverse direction of the composites are nearly equal when the ratio of length of the both sides is one. The difference in the bending strengths gets greater with increasing ratio of length of the both sides. In other words, the longitudinal bending strength increases, but the transverse bending strength decreases, with increasing ratio of length of the both sides of the initial specimen.

抄録全体を表示

Effects of extrusion conditions (temperature and speed) and cooling rate during quenching on tensile properties of 6061 aluminum alloy extrusion after T6 treatment are studied in relation to microstructures. Materials were extruded at the temperature of 673 K and 803 K and at the speed of 2.83 × 10⁻²∼2.33 × 10⁻¹ m/s, quenched at the cooling rate of 1.0∼83.3 K/s after the solution treatment at 803 K–10.8 ks, and aged at 453 K–28.8 ks. 0.2% proof stress and tensile strength are higher when the temperature and speed of extrusion are high, or when the cooling rate during quenching is high. This is related with grain size and amount of solute Mg and Si after quenching. Elongation is lower at the cooling rate of 4.3∼6.3 K/s in quenching. This is dependent on the large precipitates at grain boundaries.

抄録全体を表示