Metal matrix composites to be plastically wrought under tensile load were developed, using superplastic aluminum alloy powder and SiC particles (5μm or 20μm diameter) as matrix and reinforcement material, respectively. We discussed the effects of powder mixing process, SiC particle size, hot pressing conditions and the local heating and cooling deep drawing on the characters of the MMCs (relative density, tensile strength and plastic workability, etc.). As an example of the results, drawing ratio of MMCs containing 20μm and 25% volume fraction SiC particles attained to 2.18 by the local heating and cooling deep drawing.

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This investigation is to evaluate the possibility to combine the electromagnetic forming and the original deep drawing. The effect of punch geometry on deep drawability of aluminum alloy sheets preformed by the electromagnetic forming is compared with those preformed by the punch or unpreformed. The results are as follows: (1) Deep drawability of aluminum alloy sheets preformed by the electromagnetic forming is better than those preformed by the punch or unpreformed. This tendency is clear in case of the flat punch and elliptical punches, but not clear in case of gently elliptical punch and spherical punch. (2) Especially with the sharp elliptical punches as the ratio of axis length r_y/r_x=2.5, 3, deep drawability of A1100-O aluminum sheets preformed by the electromagnetic forming is evaluated much better than unpreformed ones. (3) The breaking strength of aluminum alloy sheets preformed by the electromagnetic forming is higher than those of preformed by the punch due to the high rate of increase of hardness with thickness strain. Good deep drawability of the former with the sharp elliptical punches and the flat punch is caused by the higher strength of aluminum alloy sheets of the former at center part and near die-r part.

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Conventional punching of sheet metal has been performed by punches and dies. If the thickness of the sheet metal is less than 0.1mm, the clearance between the punch and die has to be less than 0.005mm. As the clearance decreases, the punches and dies tend to suffer damage and wear away, and the extreme accuracy of the installation between punches and dies tend to be broken because of the reduction of punch rigidity. We have studied a new punching method for the thin sheet metal using ultrahigh pressure gas without punch. In this paper, we discuss experimentally the influence of the thickness of workpieces for the punching process of circular holes. The workpieces are sheets of aluminum, and the thicknesses are 0.3-0.8mm. The diameter of hole of dies ranges from 1.0 to 15.0mm. The punching mechanism is clearly explained. The minimum pressure required to punch the holes of given sizes could be predicted from thickness and mechanical properties of the sheet. The edge of punched holes has a large shear droop and small fracture surface. The diameter of punched holes is slightly smaller than that of dies diameters. These points are same to the results of thinner workpieces. But burrs are occurred for the workpieces over 0.6mm on thickness. This machine is suited for punching thin sheet metal.

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The formation mechanism of brittle and coarse giant intermetallic compounds in Al-Zn-Mg alloys corresponding to the 7N01 alloy containing Cr, Mn, Zr and Ti has been investigated. Two kinds of giant intermetallic compounds are observed. The first one is found to be a CrAl₇ phase into which Mn and Fe dissolve. The second one is a ZrAl₃ phase into which Ti dissolves. They crystallize as primary crystals prior to the crystallization of α-Al. The primary crystallization fields of these compounds are given as follows:
CrAl₇ phase: [%Mn]+3.25[%Cr]=0.905 at 648.8°C
ZrAl₃ phase: [%Zr]+0.909[%Ti]=0.127 at 648.8°C
Applying these equations, it is possible to predict and prevent the precipitation of the compounds during solidification.

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The formation and growth behavior of the Zr primary compounds in Al-Zn-Mg alloys corresponding to the 7N01 alloy containing Cr, Mn, Zr and Ti has been investigated. Time, t (min), necessary for crystallization of the Zr primary phase of (Zr, Ti) Al₃ from liquid is found as:
t=0.167•exp(0.143/[%Zr]+0.909[%Ti]-0.138)(at 654°C)
These compounds grow up to about 30μm within 30 minutes after beginning of crystallization. The fomation behavior of the compounds in continuous casting was also studied and discussed with the above equations. It is possible to predict and prevent the precipitation of the compounds in continuous casting by applying the above equation.

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