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題 名 | Changes of Free Energies in the Process of Discontinuous Precipitation in an Al-19.2 at.% Zn Alloy |
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作 者 | 吳世先; 楊智富; | 書刊名 | 材料科學 |
卷 期 | 22:4 1990.12[民79.12] |
頁 次 | 頁242-251 |
分類號 | 440.39 |
關鍵詞 | |
語 文 | 英文(English) |
英文摘要 | The phase transformations of discontinuous precipitation in an A1-19.2 at. Zn alloy have beeninvestigated rnorphologically and kinetically by light microscopy, electron microscopy, and X-raydiffraction. In the course of isothermal aging the metastable precipitate of a and β lamellar mixtures proceeds with constant velocity as long as there is no competing reactior. such as continuousprecipitation to-reduce the driving force. The steady state growth of discontinuous precipitationresults in colonies of lamellar mixture with approximately constant inter-lameUar spacing. Changesof chemical and surface free energies of isothermally aged specimens were determined. Effect ofvolume diffusion on the discontinuous precipitation is discussed. The diffusivities values obtainedaccording to the Petermann and Hornbogen theory for discontinuous precipitation agree well withthose determined by Hassner for stationary grain boundary diffusion. |
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