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Volume 25, Issue 11
Displaying 1-4 of 4 articles from this issue
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Tadashi MOMONO, Katsuya IKAWA1975 Volume 25 Issue 11 Pages 403-412
Published: November 30, 1975
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe structure of unidirectionally solidified Al-CuAl2 (lamellar structure), Al-Si (needle-like structure) and Al-Al3Ni (rod-like structure) eutectic alloys was studied in order to clarify the effect of artificial convection flow caused by Lorentz-interaction between a magnetic field and a direct current. Following results were obtained:
1) Artificial convection flow creates a wide equiaxed zone and causes considerable refinement of the eutectic colonies.
2) Under some definite convection flows, the columnar eutectic colonies were inclined against the stream similar to primary dendrites.
3) When the molten lead was added to the growing eutectic alloys, the solidifying interface was stopped, so that the relation between the cooling curve and solidification front was obtained. In addition to that, it has been definitely shown by the observation of solid-liquid interface morphology that the refinement of colonies is caused by the segmentation of eutectic dendrite arms or crystals of the leading phase.
4) When the interface became unstable due to turbulent artificial convection flow, the eutectic structures within the colonies showed divorced eutectic. In this case, lamellar spacing, needle spacing and rod spacing increased linearly with the reciprocal of the square root of the solidification rate.
5) With the artificial convection flow, lamellar spacing and rod spacing are broader while needle spacing is narrower.
6) Gravity segregation can be effectively diminished by the artificial convection flow.View full abstractDownload PDF (2038K) -
Hisashi SUZUKI, Motohiro KANNO, Ichiro ARAKI1975 Volume 25 Issue 11 Pages 413-421
Published: November 30, 1975
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe precipitation phenomena of the intermediate phase (θ' phase) in Al-4wt%Cu-Sn alloys containing 00.066 wt% Sn were examined at 200 and 250°C, to make clear the influence of the secondary defect structure (dislocation loop structure) which varied with Sn contents of the alloy. The results were as follows:
(1) In the binary alloy, θ' generally precipitated on dislocation loops. However, in the ternary alloys, the precipitation of θ' was confirmed to be almost independent of dislocation loops and θ' became finer and denser as Sn contents increased.
(2) As to the precipitate free zone (P.F.Z.) developed near the grain boundary, its width in the binary alloy accorded well with that of the loop free zone (L.F.Z.). However, in the ternary alloys, θ' easily nucleated within L.F.Z. in the same way as inside the grain, so that the width of P.F.Z. became very narrow.
(3) In the ternary alloys, it was observed that Sn rich phase formed at the very early stage of aging in the region close to the grain boundary as well as inside the grain, and then θ' precipitated on the Sn rich phase.
(4) In the case of direct quenching to the aging temperature, coarse θ' formed in the binary alloy where no dislocation loops formed. In contrast to this, the mode of precipitation of θ' in the ternary alloys was almost same as in usual quenching, since the Sn rich phase also formed in this case.
(5) As the results, it would be clear that the fine distribution of θ' and the enhanced precipitation at elevated temperatures so far observed in the ternary alloys were attributed to the heterogeneous precipitation of θ' on the Sn rich phase.View full abstractDownload PDF (5628K) -
Hisashi SUZUKI, Motohiro KANNO, Ichiro ARAKI, Shigeharu SAKANO1975 Volume 25 Issue 11 Pages 422-425
Published: November 30, 1975
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe Al-4wt%Cu alloys containing various amounts of Sn up to 0.101wt% were solution-treated at 520°C, quenched into iced water, kept in liquid nitrogen, and subsequently reverted at 200°C for 0.530min. The changes in electrical resistivity due to reversion were studied in detail in relation to the reverted structure by using a high resolution electron microscope. The main results were as follows:
(1) The resistivity in the quenched state was the highest in binary alloy and decreased in ternary alloys with increasing Sn contents. The resistivity decrease due to short-time reversion became smaller, while the subsequent decrease with reversion time became larger, as Sn contents increased.
(2) It was confirmed in transmission electron micrographs that, even in the short-time reversion of about 1min θ" phase formed in the binary alloy; and Sn-rich phase, in ternary alloys. Therefore, it was made clear that the uniform solid-solution with none of quench clusters was hardly obtained by usual reversion treatment at 200°C.
(3) The relation between resistivity changes due to reversion and reverted structures was discussed.View full abstractDownload PDF (735K) -
Takakazu TANAKA, [in Japanese]1975 Volume 25 Issue 11 Pages 426-438
Published: November 30, 1975
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (1657K)
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