The measurements of hardness and strain distributions on the bend points of metals suggest the forming mechanism for the bending operation.
This paper reports their distributions of the sheet products for folding operation.
The materials used for the experiments were aluminum and mild steel. At first, uni-axial strains were given to a cylindrical test piece, and then, the correspondence between the specified strains and hardness were examined.
The specified strains given for test pieces were tension, compression, and compression after tension.
Secondly, plane test pieces were cut out of the same materials to perform folding tests. After the tests, the strain and hardness distributions on the bend point of specimens were measured.
The results obtained were as follows:
1) The propagation of strain and hardness distributions was made more clear with the proceeding of operation.
2) The relations between strain and hardness on the bend point were obtained.
3) In the early stage of folding operation, the neutral plane of the specimen moved from the central position in thickness to tension side.
4) The position of moved neutral plane could be estimated from the minimum value of hardness distribution.
5) The error of the above estimation was analyzed and the mechanism due to material properties was explained.

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The effects of addition of Cu (0.65.5%) to Al-1.58wt%Mg₂Si alloys were studied by hardness measure-ments, tensile tests, and transmisson electron microscopy. It is known that the addition of Cu to Al-Mg₂Si alloys has some effects on age hardening, mechanical properties, and corrosion resistance of the alloys. This paper describes in details the effects of Cu on age hardening and mechanical properties of the alloys.
The results obtained were summarized as follows:
(1) The isothermal ageing curves of the alloys containing less than 1.5% of Cu were different from those containing more than 2%, of Cu. The former represented 1 stage ageing curves and the latter represented 2 stage ones. In general, peak hardness (maximum hardness) was higher with the increase in copper content. However, the peak hardness of the alloys containing 2% of Cu was lower than that of the alloys containing 1.5% of Cu. The time required to reach the peak hardness was longer with the increase in copper content when it was less than 1.5%; however, it was shorter with the increase in copper content when it was more than 2%.
2) It was observed by transmission electron microscopy that the precipitation hardening system of Al Mg₂Si-Cu alloys had a transition point at 2% of Cu content. It was assumed that the system was composed of Al-CuAl₂ and Al-Mg₂Si when Cu was 1.5% or less; and was composed of Al-Al₂CuMg, Al-Q (Quarternary phase), and Al-CuAl₂ when Cu was 2% or more.
3) The results of tensile tests at room and higher temperatures showed that the tensile strength was higher with the increase in copper content, but proof stress of the alloys containing 1.2 or 2% of Cu was lower than that of the alloys containing 0.6% of Cu. These facts would mainly be due to the difference of precipitates formed during the ageing.

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These investigations were undertaken concerning the effects of shapes of various round and sheet type specimens specified by JIS Z 2201 (Tension Test Pieces for Metallic Materials) on tensile properties of aluminum alloys. The propriety of sizes and shapes of these specimens in tension test pieces was discussed in connection with the effects of tensile tests on elongation percentage.
The principal results obtained were as follows:
(A) The tests conducted on sheet type specimens of JIS Nos. 1, 5, 6 and 13.
1) The lengths of reduced section of JIS Nos. 1A and 5 specimens were not satisfactory for the gauge length. Whereas, the length of that of JIS No. 13A specimen was rather longer.
2) According to the tests of Al-Zn-Mg T6 alloy, the length of reduced section of the specimen (L_c) would preferably be in the range of L_c>5.5W (W: width of the specimen). From this point of view, JIS Nos. 1 and 13A specimens would have the sizes and shapes proper for tensile test pieces.
(B) The tests conducted on round specimens of JIS Nos. 4, 10 and 14A.
3) It was desirable that the lengths of reduced section of round specimens would be determined by the following formula: L_c ≥ L₀+2D (L₀: gauge length and D: diameter of the specimen) for eliminating the effect of shoulder fillet radius on the elongation percentage in tensile tests. From this point of view, the sizes and shapes of JIS Nos. 4 and 10 specimens would not be proper; and the length of reduced section of JIS No. 14A specimen would be determined by the following formula: L_c=7D.

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Experiments were made for studies on the cellular solidification of Al-Si eutectic alloy. The results obtained are as follows:
1) It was found that the cellular eutectic structure of Al-Si alloys which resembles to the "eutectic cell" of cast iron could be revealed when an adequate solidification method was used and addition of suitable elements were made.
2) Cell boundary revealing elements may be classified into two groups. The frist group is represented by Fe which concentrates to the cell boundary as the solidification proceeds and promotes the preferential etching of the cell boundary. The second group is represented by Na which make the boundary distinct by changing the shape of eutectic Si at the boundary.
3) The eutectic cell consists of the interconnected eutectic Si buried in Al matrix. There usually are several Al grains within one eutectic cell and the cell boundary and Al grain boundary always coinsilles.
4) The addition of Na changes the morphology of not only the eutectic Si but also that of primary Si. Na makes the normally smooth surface of primary Si crystal rough and let the eutectic Si grow on it.

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The effects of additional elements, Cu, Mn, and Cr, on the change of properties during natural ageing over a period of up to three years after solution heat treatment of Al-10%Mg and Al-8%Mg-1.5%Zn alloy castings were studied by tensile tests, stress corrosion cracking tests, and metallographic examination.
Reversion of the materials, which had been subjected to room temperature ageing, was also studied by the same methods.
The results obtained were summarized as follows:
1) The change of mechanical properties during natural ageing of Al-8%Mg-1.5%Zn alloy was less than that of Al-10%Mg Alloy.
2) The change of mechanical properties during natural ageing was not only due to the formation of β' or β phase (Al₃Mg₂) in the grain boundary, but due to the presence of G. P. zone within the grains.
3) The strength of Al-8%Mg-1.5%Zn alloy was increased by the addition of Cu, Mn or Cr.
4) The addition of Cu to Al-8%Mg-1.5%Zn alloy decreased its change of elongation, but increased its susceptibility to stress corrosion cracking during natural ageing.
5) The mechanical properties and resistance to stress corrosion cracking of the both alloy castings were varied during natural ageing. However, after the reversion treatment, the mechanical properties returned to nearly the original values as quenched, while the resistance to stress corrosion cracking did not perfectly return to the as quenched conditions.

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