Dissertation > Excellent graduate degree dissertation topics show

First-principles Study of the Mechanical Properties and Elemental Partitioning Behaviors in Ni-based Superalloys

Author: WangYunJiang
Tutor: WangChongYu
School: Tsinghua University
Course: Physics
Keywords: first-principles Ni-based superalloys elastic properties ideal strength partitioning
CLC: O482.1
Type: PhD thesis
Year: 2010
Downloads: 159
Quote: 0
Read: Download Dissertation

Abstract


The high strength and creep resistance of Ni-based single crystal superalloys at-tribute to the precipitate strengthening to impede dislocations motion. The limit of pre-cipitate strengthening is determined by both the strength ofγ’ precipitate and the linear elastic properties of the y matrix. Meanwhile, the partitioning behaviors of the alloying elements have close relation with the global performance of superalloys. Therefore, the study on mechanical properties and elemental partitioning in Ni-based superalloys is of great significance in both science and engineering application.By deforming the supercells of model superalloys and their constituent phases with different specific strain vectors, we can derive their different elastic modulus via first-principles energetics calculations of stress-strain relationships. We firstly investi-gated the effect of alloying elements Ta, Mo, W, Cr, Re, Ru, Co, and Ir on the elas-tic constants and moduli of separate y andγ’ phases. Then the elastic properties of Ni/Ni3Al multi-layers were studied as rafted superalloys. Simulation results were con-sistent with the experimental observation that rafted Ni-base superalloys virtually pos-sess a cubic symmetry. The mechanical properties as a function of theγ’ phase volume fraction were also taken into consideration, and the Voigt-Reuss-Hill rule of mixture was found well to depicting the Ni-based superalloys. Finally, we used novel superal-loy models to investigate the influence of alloying elements Co, Cr, Ta, Re, and Ru on the elastic properties of ternary and quaternary Ni-based superalloys. All the calculated results are consistent with the existing experimental values. The different strengthen-ing effects of these elements were clarified. The electronic structures were provided to search the origin of strengthening effect.Further, we particularly used first-principles method to study the effect of Re on the ideal strength ofγ’-Ni3Al under both tensile and shear stresses. Re is found to be ef-fective in improving the strength of Ni3Al. The covalent-like Re-Ni bonding effectively resists the deformation of Ni3Al, and leads to a higher strength. Besides, we compared the elastic properties and ideal strengths of Ll2 Co3(Al, W) with Ni3Al to give concrete insight into the mechanical properties of Co-based and Ni-based superalloys. The ideal strength and elastic moduli of Co3(Al, W) are predicted to be higher than that of Ni3Al. The directional covalent-like Co-W bonding through d-d hybridization is the origin of excellent mechanical properties of Co3(Al, W).Finally, we investigated the partitioning behaviors of alloying elements in the Ni-based superalloys by different first-principles methods. A first-principles approach based on DFT was proposed to qualitatively study the partitioning of Re, Co, and Cr between y andγ’ phases. The effect of a second addition Ru (or Ir) on the partitioning behaviors of these elements was also predicted. The results agreed well with the ear-lier experimental works from atom probe tomography. Moreover, the different alloying mechanisms of Re, and Ru in the quaternary Ni-based superalloysγ/γ’ interface were explored. Our studies provided valuable theoretical support for the design of more advanced superalloys.

Related Dissertations

  1. Research on TCM and BICM Schemes of the Coded Modulation Technology,TN911.22
  2. First- principles calculations of doped anatase titanium dioxide photocatalytic properties,O643.36
  3. Quantifying the Effects of Weak Light on Wheat Dry Matter Production and Partitioning at Filling Stage,S512.1
  4. A Model for Predictingrowthdynamic of Cut Lilium in Greenhouse,S682.29
  5. Quantifying the Effects of Water and Nitrogen Coupling on the Growth of Standard Cut Chrysanthemum ’Jinba’ in Solar Greenhouse,S682.11
  6. Simulation Model on Development, Growth and Quality for Cut Tulip in Solar Greenhouse,S682.263
  7. First-Principles Studies of Blacl Phosphorus and LiMn2O4 as Electrode Material for Lithium Ion Batteries,TM912
  8. First-Principles Studies of Cathode Material LiMO2 （M=Co, Ni, Mn） of Lithium Ion Batteries,TM912
  9. Eu- doped α-SiAlON phosphor First-principles study,TB34
  10. First-principles study of the structure and optical properties of the high-pressure alkali metal (Li, Na, K),O521.2
  11. Theoretical Studies on the Prediction of Drug-likeness and Oral Bioavailability,R914
  12. First-principles Study on Magnetic and Optical Properties of Rutile TiO2,O614.411
  13. Preparation and Properties of ZnO-based Diluted Magnetic Semiconductors,TN304.21
  14. H.264-based wireless video transmission system research and program implementation,TN919.8
  15. Fragmentation of data security storage system applied research,TP309
  16. Based on image processing room video fire smoke recognition method,TP391.41
  17. Industry analysis of the evolution of organizational ecology - An Empirical Study of Industrial Crystal River,F224
  18. First Principles Study on Electronic and Optical Properties of TiO2 Polymorphs,TN304.21
  19. First-Principles Studies on the Interaction Between Water Molecule and Ceria Based Catalysts,O469
  20. LaB_6 optical properties of first-principles calculations and experimental study,O482.3
  21. First-principles Calculation of Magnetic Properties in ZnO-based Diluted Magnetic Semiconductors,O484.43

CLC: > Mathematical sciences and chemical > Physics > Solid State Physics > Solid nature of the > Mechanical properties and acoustic properties
© 2012 www.DissertationTopic.Net  Mobile