The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform

David H. Stjohn - One of the best experts on this subject based on the ideXlab platform.

  • Modelling of grain size transition with alloy concentration in solidified Al–Si alloys
    Journal of Materials Science, 2007
    Co-Authors: Xiangdong Yao, Cameron J. Davidson, Arne K. Dahle, David H. Stjohn
    Abstract:

    The transition in grain size with Si content in Al–Si alloys has been systematically investigated by the Cellular Automaton-Finite control Volume Method (CAFVM) to understand the operating mechanisms for this behavior. Three aspects: growth restriction factor (GRF), the Chemical Driving Force (CDF) and the constitutional undercooling (Δ T _ C ) have been demonstrated to affect the microstructure formation, and among them the Δ T _ C plays the most important role. Furthermore, it is also shown that the surface modification of the nucleant particles by silicon significantly influences the grain formation. However, the combined effects of the investigated factors on the grain size were not sufficiently strong to cause a grain size change similar to that observed experimentally. This implies that there could be other mechanisms that control the transition.

  • Modelling of grain size transition with alloy concentration in solidified Al–Si alloys
    Journal of Materials Science, 2007
    Co-Authors: Arne K. Dahle, Cameron J. Davidson, David H. Stjohn
    Abstract:

    The transition in grain size with Si content in Al-Si alloys has been systematically investigated by the Cellular Automaton-Finite control Volume Method (CAFVM) to understand the operating mechanisms for this behavior. Three aspects: growth restriction factor (GRF), the Chemical Driving Force (CDF) and the constitutional undercooling (Delta T-C) have been demonstrated to affect the microstructure formation, and among them the Delta T-C plays the most important role. Furthermore, it is also shown that the surface modification of the nucleant particles by silicon significantly influences the grain formation. However, the combined effects of the investigated factors on the grain size were not sufficiently strong to cause a grain size change similar to that observed experimentally. This implies that there could be other mechanisms that control the transition.

  • effect of solute on the growth rate and the constitutional undercooling ahead of the advancing interface during solidification of an alloy and the implications for nucleation
    Journal of Materials Research, 2006
    Co-Authors: A K Dahle, C J Davidson, David H. Stjohn
    Abstract:

    A framework is presented for modeling the nucleation in the constitutionally supercooled liquid ahead of the advancing solid/liquid interface. The effects of temperature gradient, imposed velocity, slope of liquidus, and initial concentration have been taken into account in this model by considering the effect of interface retardation, which is caused by solute buildup at the interface. Furthermore, the effect of solute concentration on the Chemical Driving Force for nucleation has been considered in this model. The model is used for describing the nucleation of Al-Si and Al-Cu alloys. It was found that the solute of Si has a significant impact on the Chemical Driving Force for nucleation in AI-Si alloys whereas Cu has almost no effect in Al-Cu alloys.

Tae-soo You - One of the best experts on this subject based on the ideXlab platform.

Kiwon Kim - One of the best experts on this subject based on the ideXlab platform.

Sung-man Lee - One of the best experts on this subject based on the ideXlab platform.

  • Effects of CeO2 incorporation on the performance of a Ta diffusion barrier for Al metallization
    Journal of Applied Physics, 1999
    Co-Authors: Jaehwa Kim, Joon Seop Kwak, Dong Soo Yoon, Hong Koo Baik, Sung-man Lee
    Abstract:

    The effects of CeO2 incorporation on the performance of a Ta diffusion barrier in the Al/Si system were investigated in the temperature range of 450–550 °C. When Ta film was deposited without CeO2 incorporation, the reaction between Ta and Al occurred at 500 °C, leading to the formation of Al3Ta. In the case of CeO2-incorporated Ta barriers, however, the reaction between Ta and Al was suppressed up to 550 °C. The suppression of the reaction of Ta with Al was attributed to the strong Chemical bonding of Ta–Ce–O or Ta–O and the amorphous-like microstructure of the CeO2-incorporated Ta barrier, followed by the reduction of the Chemical Driving Force for the initial stage of Al3Ta formation.

  • Suppression of silicide formation in Ta/Si system by ion-beam-assisted deposition
    Applied Physics Letters, 1997
    Co-Authors: Joon Seop Kwak, Hong Koo Baik, Jong-hoon Kim, Sung-man Lee
    Abstract:

    In order to increase the failure temperature of a Ta diffusion barrier for Cu, the suppression of silicide formation in a Ta/Si system by ion-beam-assisted deposition of Ta film was investigated. When the Ta layer was deposited without ion bombardment, the reaction between Ta and Si started at 600 °C. In the case where the Ta film was prepared with concurrent ion bombardment, however, the silicide formation was retarded up to 700 °C. The suppression of Ta silicide formation can be attributed to a densification of grain boundaries in the Ta film by ion bombardment, followed by a reduction of the Chemical Driving Force for the initial stage of silicide formation. The Ta diffusion barrier deposited by ion-beam-assisted deposition effectively suppressed the reaction between Si and Cu layers up to 650 °C for 30 min.

E. A. Wilson - One of the best experts on this subject based on the ideXlab platform.

  • Chemical Driving Force shear moduli of ferrite and metastable austenite and strain energy for γ α transformation in pure iron
    Materials Science and Technology, 1995
    Co-Authors: E. A. Wilson
    Abstract:

    AbstractThe Chemical Driving Force/unit volume ∆Gv for the γ→α.transformation. in pure iron is computed as a function of undercooling. Similarly, the strain δ accompanying the transformation at different temperatures is also calculated from lattice parameter measurements. Shear moduli μα of ferrite and metastable austenite μγ are derived from various sources. At temperatures down to the Curie temperature (768°C), μα and μγ are very similar, and enable the strain energy/unit volume W to be calculated from the expression W=2 (μα+ μγ)δ2. The data give the metastable equilibrium temperature T;amp;#x2032;0 for the massive ferrite transformation as 1156 K. The distinction between equiaxed ferrite, massive ferrite, and Widmanstatten ferrite is discussed.MST/3138

  • Chemical Driving Force, shear moduli of ferrite and metastable austenite, and strain energy for γ→α transformation in pure iron
    Materials Science and Technology, 1995
    Co-Authors: E. A. Wilson
    Abstract:

    AbstractThe Chemical Driving Force/unit volume ∆Gv for the γ→α.transformation. in pure iron is computed as a function of undercooling. Similarly, the strain δ accompanying the transformation at different temperatures is also calculated from lattice parameter measurements. Shear moduli μα of ferrite and metastable austenite μγ are derived from various sources. At temperatures down to the Curie temperature (768°C), μα and μγ are very similar, and enable the strain energy/unit volume W to be calculated from the expression W=2 (μα+ μγ)δ2. The data give the metastable equilibrium temperature T;amp;#x2032;0 for the massive ferrite transformation as 1156 K. The distinction between equiaxed ferrite, massive ferrite, and Widmanstatten ferrite is discussed.MST/3138