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Volume 25, Issue 3
Displaying 1-5 of 5 articles from this issue
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Tadahisa NAKAMURA, Masanori UEKI, Shiro HORIE1975 Volume 25 Issue 3 Pages 81-87
Published: March 30, 1975
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSSubgrain size of high purity aluminum deformed in torsion at various temperatures and strain rates was measured, and room temperature compression tests were carried out on these samples with subgrains ranging 2-30μm. The retention of subgrains developed during warm and hot working leads to the enhancement of mechan-ical properties. The room temperature strength of substructure strengthened materials correlates well with the size of the retained subgrains and is shown to follow the modified Hall-Petch relation: δ=δo+KD-1/2+kd-m. Here, δo and KD-1/2 are the usual Hall-Petch terms and kd-m is the strength increment due to the presence of a hot-worked substructure. The exponent m was observed to be 1 for this material. The strength increment due to the presence of subgrains was observed to be proportional to a power of the temperature-compensated strain the in hot working. Thus a simple correlation exists between the high temperature deformation conditions and rate room temperature strength.
At grain sizes less than about 7 μm, strengthening due to subgrains appear to be more effective than grains of the same size. This suggests that substructure-strengthening may be more important than strengthening by grain refinement in this grain size range.View full abstractDownload PDF (1999K) -
Toshiyasu FUKUI1975 Volume 25 Issue 3 Pages 88-95
Published: March 30, 1975
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSEffect of grain-refining elements such as Ti, Zr and Ti-B on toughness of Al-Mg-Mn alloy welds was studied by measuring the notch-tensile and yield strength ratios, Charpy impact value and crack propagation energy in modified Navy tear tests.
Tensile and yield strengths of unnotched specimens increased with additions of grain-refining elements. How-ever, the notch-tensile and yield strength ratios decreased slightly because of the reduction of tensile strength of notched specimens. Charpy impact value showed less variation with additions of grain-refining elements, but the value decreased in case of excess additions of these elements. On the other hand, crack propagation energy in the tear test decreased with additions of grain-refining elements.
Among Ti, Zr and Ti-B, Ti-B addition had the most harmful influence. The reduction of notch toughness and tear resistance with additions of these elements seems to be caused by the formation of insoluble compounds.View full abstractDownload PDF (2829K) -
Masao IKEDA, Kiyoshi TERAYAMA1975 Volume 25 Issue 3 Pages 96-102
Published: March 30, 1975
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSStudies were made on the effect of alkali additions (CaO, dolomite, cabide cinder), the properties of Mg(OH)2, the production of artificial dolomite and the yield of metallic magnesium, and following results were obtained.
1) Except CaO, there is no difference in the sedimentation velocity of Mg(OH)2 between dolomite and carbide cinder as alkali additions.
2) The temperature rise in hydration of artificial dolomite by the wet method is larger than that by the dry method, and this agrees with the tendency of the yield of metallic magnesium.
3) The yield of magnesium is strongly influenced by the purity of CaO used for the production of artificial dolomite.
4) There is no large difference in the activation energy and the purity of metallic magnesium between the reducing reaction of natural dolomite and that of artificial dolomite.View full abstractDownload PDF (774K) -
Yo KOJIMA, Tsuneo TAKAHASHI1975 Volume 25 Issue 3 Pages 103-107
Published: March 30, 1975
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe purpose of this paper was to discuss the relationship between stress corrosion cracking and surface energy of Al–4%Zn–1%Mg and Al–4%Zn–2%Mg. The surface energy was calculated by means of the approach used by Coleman et al., i.e., the relationship between fracture stress and grain size. The effect of grain size on the resistanse to stress corrosion cracking was also investigated.
The results obtained were summarized as follows.
1) The values of effective surface energy of Al-4%Zn-1%Mg and Al-4%Zn-2%Mg in the corrosive medium were 0.63 × 103 and 0.28 × 103 erg/cm2, respectively.
2) The result that the effective surface energy of Al-4%Zn-1%Mg was larger than that of Al-4%Zn-2%Mg, corresponded with the observation that the former showed better resistanse to stress corrosion cracking than the latter.
3) The susceptibility to stress corrosion cracking of Al-4%Zn-1%Mg and Al-4%Zn-2%Mg decreased with the increase of grain size.View full abstractDownload PDF (760K) -
Yoichi ISHIDA1975 Volume 25 Issue 3 Pages 108-122
Published: March 30, 1975
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (3801K)
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