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Volume 23, Issue 8
Displaying 1-6 of 6 articles from this issue
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Shigeo OYA, Yuji MATSUURA, Shizuo SUZUKI, Eiichi NAKATA1973 Volume 23 Issue 8 Pages 345-353
Published: August 30, 1973
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSThe effect of high pressure solidification on the fatigue strength of cast aluminum and aluminum alloys was studied.
(1) The fatigue limit of pure aluminum is hardly influenced by high pressure solidification.
(2) High pressure casting of an eutectic Al-Si alloy (JIS AC3A and AC4C)
(3) The fatigue limit of an Al-Cu alloy (AC1A), T-6 treated, is increased by approximately 10% by casting under high pressure.
(4) High pressure casting produces an increase of the fatigue limit of an Al-Mg alloy (AC7A), although the pressure larger than 2, 000kg/cm2 has an inverse effect caused by pronounced segregation.View full abstractDownload PDF (4342K) -
Hiroshi NAKAMURA1973 Volume 23 Issue 8 Pages 354-359
Published: August 30, 1973
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSThe dissolving rate and the hardness were measured upon isothermal aging, reversion, and re-aging of Al-Mg2Si alloys. The dissolving rate was measured by hydrogen evolution when specimens were immersed in 1/10N-NaOH solution at 20°C. The results obtained were as follows:
(1) It was found that the amount of evolved hydrogen was proportional to immersion time.
(2) The increase of hardness was rapid at the early stage of the aging and became slower as the aging proceeded. The dissolving rate depended on aging time in a complex manner; it was largest in the as-quenched state, decreased with aging, and again showed a slight increase after showing a minimum.
(3) Reversion treatment softened the aged specimen almost completely. The dissolving rate was increase by reversion except cases when it had been at or close to a minumum upon the first aging.
(4) The specimen, which had been aged to the minumum dissolving rate state, showed a significantly slow rate of hardness increase and dissolving rate decrease upon re-aging. The change of the hardness was not consistent with the change of the dissolving rate upon reversion. However, good correspondence betweer the hardness and the dissolving rate was found at re-aging. It was shown by the dissolving rate measrement that there existed a special state with respect to a structure of Al-Mg2Si alloys.View full abstractDownload PDF (710K) -
Hiroshi NAKAMURA1973 Volume 23 Issue 8 Pages 360-367
Published: August 30, 1973
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSThis paper studied aging processes of Al-1.1-1.6%Mg2Si alloys by hardness and electrical resistivity measurements and on electron microscopy. After solution treatment at 580°C, specimens were quenched into water at 1±0.2°C and aged at 20-90°C. Reversion treatment was performed at 285, 320 and 380°C, as determined by preliminary experiments. The results obtained are as follows:
(1) Both hardness and resistivity increased on aging.
(2) Hardness increase, attained by aging, was recovered nearly completely by reversion when reversion time was within a certain period. This period depended on aging and reversion temperatures. Resistivity increase due to aging was recovered completely by reversion at 285, 320 and 380°C, whatever the aging stage was. Thus, the time required for complete reversion was determined by the resistivity and the hardness on re-aging at the initial aging temperature. At 380°C, the complete reversion time determined by the resistivity measurement agreed with that determined by the hardness measurement. However, on 285°C and 320°C reversion treatment, there was a difference between the reversion time determined by hardness measurement and that by resistivity measurement.
(3) When aging was arrested in the early stage at the initial aging and reversion was performed at 285°C, hardening at re-aging progressed very slowly.View full abstractDownload PDF (1408K) -
Shiro SATO1973 Volume 23 Issue 8 Pages 368-375
Published: August 30, 1973
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSEffects of specimen dimensions on elongation at tensile tests were studied for aluminum alloy sheets, 3.8mm thick 6061-T6 alloy and 6.2mm thick 7075-T6 alloy. The optimum size and shape of tensile specimens were discussed, based on the present and the previous studies. The principal results obtained are as follows:
(1) From the longitudinal strain distribution of the specimens, various alloys can be classified into three group; (a) Barba type, (b) Oliver type and (c) modied Barba type.
(2) The percentage elongation of materials of the Barba type is reasonably constant when the ratio of the gage length to the square root of the cross sectional area L0/√A is kept constant.
(3) Even when L0/√A is constant, the percentage elongation of the Oliver type specimens increasess slightly as the ratio of the reduced section length to the specimen width, Lc/W, incrases. Lc/W, not less than 5.5, is desirable for this type of materials.
(4) Some modified Barba type specimens shows the Lc/W dependence of the percentage elongation, similar to that exhibited by the Oliver type.
(5) The length of the necked region can be measured from the strain distribution in the Barba and the modified Barba type materials. It was shorter than 5√A for most materials. Thus, the gage length should be larger than 5√A.
(6) The shoulder region, lf costraining the strain distribution, is 0.2-0.4 times W when W/T>4. In order to eliminate the effect of the shoulder on the elongation, Lc should be larger than L0+0.8 W. lf/W increases as W/T decreases and nearly equals to 1 in the square cross sectioned specimens. Thus, when W/T is nearly equal to 1, Lc should be taken as L0+2W.View full abstractDownload PDF (714K) -
Tsuneo TAKAHASHI, Yo KOJIMA, Kiyoshi TAKANISHI1973 Volume 23 Issue 8 Pages 376-382
Published: August 30, 1973
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSFormation and growth of precipitates in a Mg-3.6wt.%Zn alloy during aging between room temperature and 140°C were examined by means of an X-ray diffraction method. Two different types of G.P. zones as well as intermediate phases were formed during the aging. The precipitation process occurred in the following order: supersaturated solid solution→G.P. [1]→G.P. [2]→β'1→β'2→β. The plate-like G.P. [1], formed by the aging below 60°C was parallel to {1120} planes of the magnesium matrix. The G.P. [2] appeared in the form of an oblate spheroid on the basal plane of the matrix below 80°C. The rod-shaped β'1 was perpendicular to the basal plane, while the β'2, the other intermediate phase of rod shape, was formed perpendicular to {1010} planes of the matrix. The β'2 which had the same composition, structure, and shape as the β'1, was thought to be formed by the transformation stress of the β'1 phase. Hardening of the present alloy was induced by the precipitation of the β'1 and β'2, while it was hardly affected by the formation of the G.P. zones.View full abstractDownload PDF (2138K) -
Yoshitsugu MISHIMA1973 Volume 23 Issue 8 Pages 383-387
Published: August 30, 1973
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDownload PDF (822K)
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