| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1988: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1987: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
The project entitled "Improvement of Mechanical Properties of an Al-Li Alloy by Means of Additional Elements" has been completed under the Grant-in-Aid for Scientific Research by The Ministry of Education, Science and Culture. Abstract of results obtained is as follows:
(1) It has been found that a complex precipitation takes place during duble aging in Al-Li alloys containing Zr, Ti or Hf. The complex precipitates consist of Al_3M (M:Zr, Ti or Hf) surrounded by the Al_3Li, which grows during the second aging.
(2) All precipitates are found to be metastable phase of ordered L1_2 structure.
(3) Role of each element in the aging procedure has been investigated by microstructural observation by an transmission electron microscope. Results are summarized as follows:
Zr, Ti or Hf : Each of these elements precipitates as Al<@23<@D2M during g the first aging at high temperature. This precipitates acts as the nuclei of the Al-<@D23@>D2Li formed during the second step of aging.
Cr : This precipitates heterogeneous at grain boundaries as Al_7Cr at very early stage of the first aging. The precipitate pinned down the grain boundary, so that the precipitation of the grain boundary reaction type (discontinuous precipitation) was completely suppressed. As a result, area covered by the continuous precipitation of fine spherical particles increased, then the maximum hardness is improved remarkably. Si : This accelerates the continuous precipitation in grains, so that it also contributes the improvement of mechanical properties of these aged alloys.
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