新聞資訊
實用型數值回歸法在三元鋁合金互擴散系數計算中的應用
發布人：上海艾荔艾合金股份有限公司www.shailiai.cn
更新時間：2016-05-09
制備了 bcc 結構 Al-Fe-Mn 和 fcc 結構 Al-Cu-Ni 三元鋁合金單相固態半無限長和有限長 (或薄膜型) 擴散偶, 通過 EPMA 測得相應成分-距離曲線, 并采用實用型數值回歸法計算了相應合金體系 1273 K 時隨成分變化的互擴散系數, 所得結果均滿足熱力學穩定條件.
實用型數值回歸法在三元鋁合金互擴散系數計算中的應用APPLICATION OF PRAGMATIC NUMERICAL INVERSE METHOD IN?COMPUTATION OF INTERDIFFUSION COEFFICIENTS IN Al TERNARY?ALLOYS?
制備了 bcc 結構 Al-Fe-Mn 和 fcc 結構 Al-Cu-Ni 三元鋁合金單相固態半無限長和有限長 (或薄膜型) 擴散偶, 通過 EPMA 測得相應成分-距離曲線, 并采用實用型數值回歸法計算了相應合金體系 1273 K 時隨成分變化的互擴散系數, 所得結果均滿足熱力學穩定條件. 基于所測得互擴散系數及 Fick 第二定律, 重現了實驗測定的成分-距離曲線, 證實了所獲得互擴散系數的可靠性. 進一步分析結果表明, 該實用型數值回歸法不僅可以高效準確地計算單相三元擴散偶隨成分變化的互擴散系數, 還能很好地解決傳統方法不能處理的情況, 如擴散通道上無交點的擴散偶和有限長 (或薄膜型) 擴散偶等。
Owing to excellent mechanical properties, Al alloys are widely used in aerospace, automotive and?civil industry. In order to optimize the properties and performance of the currently used Al alloys and/or even?design novel Al alloys, the quantitative description of the microstructure during alloys preparation is the key. In?recent years, the phase-field simulation coupling with the CALPHAD thermodynamic and atomic mobility?databases has become an effective way to quantitatively simulate the microstructure evolution. So far, the accurate?thermodynamic database for Al alloys has been established. However, it is not the case for atomic mobility?database for Al alloys. The major obstacle lies in lack of reliable diffusion coefficients in ternary and higher-order?Al alloys, and thus there is an urgent need to remedy this situation. In the present paper, several semi-infinite and?finite (thin film) single-phase solid-state diffusion?couples in bcc Al-Fe-Mn and fcc Al-Cu-Ni alloys?were first prepared. The concentration profiles for all?the diffusion couples were then measured by means?of EPMA. After that, the pragmatic numerical?inverse method, which has been recently developed?for high-throughput determination of the?interdiffusion coefficients in ternary system, and?validated in several systems, was employed to compute the composition-dependent interdiffusivities in the?corresponding systems at 1273 K. In order to eliminate the possibility that different interdiffusivities at the same?composition would be obtained from different sets of diffusion couples, only one set of adjustable parameters?were used for one system. All the obtained interdiffusivities satisfy the thermodynamic constrains. On the basis of?the determined interdiffusivities as well as Fick’s second law, all the experimental concentration profiles were?reproduced nicely via numerical simulation, which verifies the reliability of the determined interdiffusivities. The?further analysis indicates that the pragmatic numerical inverse method can not only realize the determination of?reliable composition-dependent interdiffusion coefficients in ternary diffusion couples, but also cover the cases,?which cannot be dealt with by the traditional Matano-Kirkaldy method, such as the diffusion couples without?intersection along their diffusion paths, and the finite (thin film) diffusion couples. In addition, the comparison?between the interdiffusivities from semi-infinite diffusion couples and those from finite (thin film) diffusion?couples was made, and the probable reason for their difference was also pointed out. All the presently obtained?interdiffusivities in bcc Al-Fe-Mn and fcc Al-Cu-Ni alloys will be utilized to develop the accurate atomic mobility?databases in ternary Al-Fe-Mn and Al-Cu-Ni systems in the next step.
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