Gibbsite was dehydrated in a suspension heater at a high heating velocity of an order of 10⁴°C/s. One-stage dehydration products are obtained without forming boehmite and γ-Al₂O₃. The crystal structure of the products changes from χ-Al₂O₃ to α-Al₂O₃ via pseudo γ-Al₂O₃ as the temperature of heating gas rises. The product with a surface area 300m²/g or more transforms into bayerite and pseudo boehmite by water treating for 96h at 80°C. The χ and γ-Al₂O₃ to α-Al₂O₃ phase transformation follows zero-order kinetics at the initial stage of the reaction. The dehydration products have activation energies higher than χ or γ-Al₂O₃. The rate of gibbsite to α-Al₂O₃ phase transformation in the suspension heater is much higher than that of the dehydration products in the electric furnace.

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The surface of the alloy solution treated at 540°C for 20h and water quenched was scratched by a diamond scriber before and after aging at 390°C for 20h. Scanning electron microscopy was carried out on the precipitate particles in the deformed surface layers in the successive stages of metal surface dissolution by electropolishing. Scanning electron microscopy was also carried out on the oblique section of the scratching tacks prepared by emery paper scratching followed by electropolishing. If scratched prior to the aging treatment, the degree of deformation in the deformed surface layer is estimative quantitatively by the present method. If scratched after the aging treatment, the degree of deformation is also estimated by the method. A[110]fiber structure is found in the region of the heavily deformed superficial layer corresponding to the layer formed under compressive stress more than about 25kg/mm².

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Scanning electron microscopy and transmission electron microscopy using plastic-carbon replicas were carried out of the fine-grained Al-Zn eutectoid alloys tensile deformed at different strains at 230 to 300K. Both grain boundary sliding (GBS) and crystallographic slip (CS) occur in the normal deformation region in which the alloys deform at low temperature (230-253K) and high stress. The crystallographic slip is more predominant than GBS in the alloys having coarse grain size (L>2μm), but GBS predominates in the alloys of fine grain size (L<1μm). Grain boundary cavities formed by GBS tend to grow and connect to each other with increase of strain. Although both GBS and CS occur in the transition region in which the alloys deform. at intermediate temperature (280-300K) and intermediate stress, GBS is always more predominant than CS. An isotropic equiaxial structure having average grain size 2 to 4μm is preferable for plastic working. The fracture mode is also described.

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Two stage strain path deformotion increases the limit strains to a greater degree than single strain path deformation. The equibiaxial straining followed by uniaxial straining (two stage strain path I) increases the limit strain in the range of the plane strain deformation. The uniaxial straining followed by biaxial straining (two stage strain path II) increases the limit strains in the range of stretch-forming. The sheet thickness has an indistinct effect on the forming limit curve, if the difference in thickness is within 10 per cent.

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Square holes with radiuses of curvature at the corners 2, 4, 6, 8 and 10mm were punched in A1100P-O and A1100P-H24 sheets 2.0, 2.5 and 3.0mm in thickness. The punching process for square holes with corner radiuses 2, 4 and 6mm is different from that for square holes with corner radiuses 8 and 10mm. The H24-sheets have better punching workability than the O-sheets. When punching is impossible, the radius of curvature at the limit of rubber deformation ρ is from 8.0 to 11.0mm. The minimum radius of ρ (the maximum deformation of rubber) is 8.0mm. Difference in dimension between the punched square hole and the die hole is greatest at R=2mm. The dimension of punched square holes is unsusceptible to the flaws on the rubber surface formed by about 100 times of punching.

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Aluminum sheets were anodically oxidized in phosphoric acid under the conditions of (1) D. C. 20V electrolysis, (2) A. C. 20V electrolysis, (3) current recovery from D. C. 30V to 20V, and (4) stepwise elevation of A. C. voltage 5-10-15-20V and were colored in nickel sulfate bath. The spectral selectivity and the film structure were measured by spectroscopy and scanning electron microscopy respectively. The color-anodized surfaces formed under the above conditions have more complicated structures in order of (1)<(2)<(3)<(4). The spectral selective absorptivity is in good agreement with the structural complication in order of (1)<(2)_??_(3)<(4). The more complicated structure of the color-anodized film ensures the spectral selectivity more intensified.

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