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Volume 20, Issue 10
Displaying 1-6 of 6 articles from this issue
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Hirozo KIMURA, Osamu NAKANO1970 Volume 20 Issue 10 Pages 481-489
Published: October 30, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe effects of addition of V, Nb, Ta, Cr, Mo and W individually in small amounts to aluminum of high purity were studied by means of hardness measurements, tensile tests and transmission electron microscopy.
The results obtained were as follows:
(1) The alloying elements had little effects in improving mechanical properties, softening temperature and micro-structure of aluminum, when they were added in the amounts within their solid solubility limits at the temperature of annealing.
(2) Considerably great effects were given, when the alloying elements were added in the amounts beyond their solid solubility limits at the temperature of annealing. There were observed increase of tensile strength, elevation of softening temperature and other effects with the increase of alloying elements.
It was shown by electron microscopy that the structures of the above specimens 50% cold worked and those during annealing after cold working were more complicated as compared with the structure of the paragraph (1).
(3) Addition of chromium to aluminum was more effective than V, Nb, Ta, Mo and W in increasing tensile strength and elevating softening temperature. Hot hardness value of Al-0.41 at.%Cr alloy was little decreased with temperature up to 200°C. However, it was nearly three times as high as that of pure aluminum at 400°C.View full abstractDownload PDF (3720K) -
Goro OMORI, Shigeru MATSUO, Hiroshi ASADA1970 Volume 20 Issue 10 Pages 490-497
Published: October 30, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe ageing characteritics of Mg-0.2wt.%Ce alloy which has the highest workability among the alloys of Mg-Ce system, were studied by means of hardness measurements and transmission electron microscopy.
In isochronal ageing of the alloy cold worked after solution heat treatment, softening which would be due to dislocation rearrangement occurred up to about 75°C, and then, hardening due to precipitation of Mg9Ce gradu ally took place in the range up to about 200°C.
In isothermal ageing in a temperature range of 100200°C, an age-hardening effect was found in the alloy cold worked after solution heat treatment, but little effect was found in the alloy with no cold working after the treatment.
In the former alloy, the precipitation of coherent spherical particles preferentially occurred on dislocations and developed to plates on (1120) planes in magnesium matrix. Whereas, in the latter alloy, preferential precipitation of Mg9Ce was observed on grain or sub-grain boundaries, but not in the matrix.
Split ageing behavior was also studied for the former alloy. The pre-ageing treatment was performed at 50 and 100°C immediately followed by the final ageing treatment at 200°C. When the ageing time at the pre-ageing was shorter, the hardness was higher at a very early stage of the final ageing. Although same softening more promptly occurred after reaching the maximum hardness, the maximum hardness value in the final ageing was lower when the pre-ageing time was longer. The hardness was nearly constant in the last stage of the final ageing, independent of pre-ageing time. However, the value for the specimens pre-aged at 100°C was somewhat lower than that for the specimens pre-aged at 50°C.
The improvement of mechanical properties of the alloy can be explained by the locking of dislocation due to the particles preferentially precipitated on the alloy.View full abstractDownload PDF (3520K) -
Studies on stress corrosin cracking of Al-Zn-Mg alloys (2nd report)Tsuneo TAKAHASHI, Yo KOJIMA1970 Volume 20 Issue 10 Pages 498-503
Published: October 30, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSIt was reported in the previous paper that the resistance to stress corrosion cracking and mechanical properties of Al-Zn-Mg alloys depend upon conditions of heat treatment. The stress corrosion cracking of Al-4.2%Zn-1.4%Mg alloy was tested by cantilever loading system in aqueous solution of 5.3% NaCl+0.3%H2O2.
The results obtained were summarized as follows:
(1) The resistance to stress corrosion cracking was increased, but the mechanical strength was decreased with the decrease of quenching rate.
(2) The resistance to stress corrosion cracking was not always increased with the drop of temperature of solution treatment.
(3) There was not always found any correlation between the resistance to stress corrosion cracking and the width of precipitate-free-zone.View full abstractDownload PDF (3306K) -
Effect of short time annealing on resistance to strees corrosion cracking of Al-Zn-Mg ternary alloysStudies on stress corrosion cracking of Al-Zn-Mg alloys (3rd report)Tsuneo TAKAHASHI, Yo KOJIMA1970 Volume 20 Issue 10 Pages 504-508
Published: October 30, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSAn equivalent short time annealing experiment was carried out to study the heating effect on heat-affected zone of Al-Zn-Mg alloys by welding. Mechanical properties and resistance to stress corrosion cracking were investigated after the annealing.
The results obtained in T4, T6 and T7 treated alloys were as follows:
(1) In T6 and T7 treated alloys, the recovery of strength was not clearly found by ageing treatment after the annealing at 250°C.
(2) After the annealing at above 350°C for only 1 min., the properties before the annealing was perfectly changed.
(3) It was confirmed that there was a close correlationship between the resistance to stress corrosion cracking and the structure of alloys aged after the annealing.
(4) The strength of the alloys was increased with the increase of cooling rate after the annealing. However, the stress corrosion resistance was increased with the decrease of cooling rate after the annealing.View full abstractDownload PDF (790K) -
Shozo YOSHIOKA, Yutaka NAKAYAMA, Norio HOSOKAWA1970 Volume 20 Issue 10 Pages 509-519
Published: October 30, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSSerrated yielding was observed in quenched Al single crystals and quenched dilute Al-Zn single crystals, which had been deformed by tension at room temperature.
The characteristics of serrated yielding of these crystals were investigated by its dependence on quenching temperature, tempering temperature, and strain rate, and appearance of slip lines.
The principal results obtained were as follows:
(1) The serrated yielding was observed only in single crystals containing Frank-sessile dislocation loops as secondary lattice defects.
(2) The dependence of the serrated yielding on quenching and tempering temperatures would by attributed to sizes and densities of the Frank-sessile dislocation loops.
(3) The dependence of the yielding on strain rate would be attributed to the interaction between moving dislocations and Frank-sessile dislocation loops.
(4) It would be concluded from these experiments that the serrated yielding may be controlled by superjogs formed by the interaction between the moving dislocations and the Frank-sessile dislocation loops.View full abstractDownload PDF (2153K) -
Keiji OKUSHIMA1970 Volume 20 Issue 10 Pages 520-529
Published: October 30, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (1335K)
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