NIMS Award Symposium 2023｜Abstracts

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Numerical Simulations to Analyze the Corrosion Behavior of M M. Kadowaki 1 Numerical Simulations to Analyze the Corrosion Behavior of M1 Research Center for Structural Materials, National Institute for Materials Science (NIMS) M. Kadowaki 1 In automobile industry, lightweighting has become an important concept to reduce energy 1 Research Center for Structural Materials, National Institute for Materials Science (NIMS) consumption. The weight of the vehicles can be reduced by utilizing lightweight materials, such as Al alloys, as an alternative of steels. It results in an inevitable increase in the percentage of Al alloy/steel In automobile industry, lightweighting has become an important concept to reduce energy coupled structures in automobile components. However, galvanic corrosion between Al alloys and steels consumption. The weight of the vehicles can be reduced by utilizing lightweight materials, such as Al is a fundamental problem. When Al alloy/steel coupled structures exist in corrosive environments, the alloys, as an alternative of steels. It results in an inevitable increase in the percentage of Al alloy/steel Al alloys and steels typically act as anodic and cathodic sites, respectively, to cause galvanic corrosion. coupled structures in automobile components. However, galvanic corrosion between Al alloys and steels That is, corrosion damage preferentially occurs on Al alloys, while steels are basically protected from is a fundamental problem. When Al alloy/steel coupled structures exist in corrosive environments, the corrosion. In addition, it has been reported that when the anodic reaction on the Al alloys is insufficient, Al alloys and steels typically act as anodic and cathodic sites, respectively, to cause galvanic corrosion. corrosion reactions (self-corrosion) also occur on the steels. However, it is difficult to simultaneously That is, corrosion damage preferentially occurs on Al alloys, while steels are basically protected from evaluate both the galvanic and self-corrosion rates based only on the experimental data. In this study, corrosion. In addition, it has been reported that when the anodic reaction on the Al alloys is insufficient, the corrosion behavior of Al alloy/steel couples was analyzed by using both finite element method corrosion reactions (self-corrosion) also occur on the steels. However, it is difficult to simultaneously (FEM) simulations and experiments. In particular, close attention was given to the balance between the evaluate both the galvanic and self-corrosion rates based only on the experimental data. In this study, galvanic corrosion and self-corrosion. the corrosion behavior of Al alloy/steel couples was analyzed by using both finite element method (FEM) simulations and experiments. In particular, close attention was given to the balance between the galvanic corrosion and self-corrosion. Segregation Engineering of Structural M I. Ohnuma, Toru HARA and Takahito OHMURA Segregation Engineering of Structural MResearch Center for Structural Materials, National Institute for Materials Science (NIMS) I. Ohnuma, Toru HARA and Takahito OHMURA It is well-known that alloying elements and impurities in polycrystalline materials segregate in the Research Center for Structural Materials, National Institute for Materials Science (NIMS) grain boundary (GB), which causes great influence on the microstructure formation, mechanical properties, etc. of structural materials. Recently, experimental studies on the GB segregation using atom It is well-known that alloying elements and impurities in polycrystalline materials segregate in the probe tomography were performed and tremendous results of quantitative measurement of GB grain boundary (GB), which causes great influence on the microstructure formation, mechanical segregation were reported. However, precise thermodynamic calculation of the GB segregation in properties, etc. of structural materials. Recently, experimental studies on the GB segregation using atom practical materials containing multiple alloying elements and impurities has not been carried out yet. In probe tomography were performed and tremendous results of quantitative measurement of GB the present study, calculation method and calculated results of the GB segregation in structural materials segregation were reported. However, precise thermodynamic calculation of the GB segregation in by CALPHAD method will be presented. practical materials containing multiple alloying elements and impurities has not been carried out yet. In The parallel tangent law proposed by Hillert was extended to the multicomponent system up to 10 the present study, calculation method and calculated results of the GB segregation in structural materials alloying or impurity elements and applied to calculate the segregated compositions using the following by CALPHAD method will be presented. conditions for the chemical potential of constituent elements: The parallel tangent law proposed by Hillert was extended to the multicomponent system up to 10 GB−𝜇𝜇𝜇𝜇𝑋𝑋𝑋𝑋2alloying or impurity elements and applied to calculate the segregated compositions using the following where M represents solvent and X1, X2, ⋯ represent alloying or impurity elements. The GB phase was conditions for the chemical potential of constituent elements: supposed to have random structure which has the free energy identical to that of the liquid phase. The GB−𝜇𝜇𝜇𝜇𝑋𝑋𝑋𝑋2Gibbs energy of the liquid and matrix phases was taken from Thermo-Calc using thermodynamic where M represents solvent and X1, X2, ⋯ represent alloying or impurity elements. The GB phase was databases via TQ-Interface and used for the calculation. The effect of (1) grain size, (2) grain boundary supposed to have random structure which has the free energy identical to that of the liquid phase. The energy, and (3) diffusion of alloying elements were also considered in the present calculation. Gibbs energy of the liquid and matrix phases was taken from Thermo-Calc using thermodynamic databases via TQ-Interface and used for the calculation. The effect of (1) grain size, (2) grain boundary energy, and (3) diffusion of alloying elements were also considered in the present calculation. ======70PP44--0033 PP44--0033 PP44--0044 PP44--0044 GB−𝜇𝜇𝜇𝜇Mmatrix𝜇𝜇𝜇𝜇MGB−fiMmatrixonMPoster Presentation ｜NIMS Award Symposium 2023GB−𝜇𝜇𝜇𝜇𝑋𝑋𝑋𝑋1matrix𝜇𝜇𝜇𝜇𝑋𝑋𝑋𝑋1GB−𝐼𝐼𝐼𝐼𝑋𝑋𝑋𝑋1matrix𝜇𝜇𝜇𝜇𝑋𝑋𝑋𝑋1aterials by CALPHAD Materials by CALPHAD M P4 ｜ Modelingmatrix𝜇𝜇𝜇𝜇𝑋𝑋𝑋𝑋2matrix𝜇𝜇𝜇𝜇𝑋𝑋𝑋𝑋2etallic Materials etallic Materials ethod ethod ⋯ ⋯