Dissertation > Excellent graduate degree dissertation topics show

The Study on the Synthesis and Grain Refinement of Al-Ti-B-C Master Alloy

Author: ZhangSen
Tutor: WangJun
School: Shanghai Jiaotong University
Course: Materials Science
Keywords: Al-Ti-B-C master alloy TiB2 TiC grain refinement refinement mechanism
CLC: TG146.21
Type: Master's thesis
Year: 2012
Downloads: 161
Quote: 0
Read: Download Dissertation

Abstract


In this thesis, master alloys were prepared by high-energy ultrasound treatment process at low temperature and induction melting process at high temperature respectively. High purity aluminum, sponge Ti and B4C particles were used as reactants, in accordance with the composition ratio of Al-5Ti-1B4C. And the materials analysis facilities, such as X-ray diffractometer, scanning electron microscopy and energy dispersive spectroscopy, were used to observe and identify the existence and morphology of production phases. The effect of different process parameters on the morphology and size distribution of the TiAl3, TiB2 and TiC particles in master alloys were carefully studied. The thermodynamic and kinetic mechanisms of the Al-5Ti-1B4C reaction system were analyzed by the calculation and experimental results. Finally, the grain refinement performance of the master alloy synthesized by different process were well researched and the refining mechanisms of Al-Ti-B-C master alloy were discussed. The main conclusions can be summarized as follows:⑴The thermodynamic calculations showed that the reaction, 3Ti + B4C = 2TiB2 + TiC, has the lowest enthalpyΔrH0 and Gibbs free energy changeΔrG0 in the Al-5Ti-1B4C system. So, this reaction may react in the system spontaneously.⑵There was no evidence of the reaction between Ti and B4C in the high energy ultrasound treatment process at 850℃. Such master alloys synthesized by ultrasound treatment are only composed with Al and TiAl3. The block TiAl3 phase has a average size less than 20μm. With the increase of the times and duration of ultrasound treatment, the block TiAl3 tend to be finely dispersed in the matrix, and become a spherical shape.⑶The wettability of Al/B4C interface is improved significantly by rising reaction temperature. The Al-Ti-B-C quaternary master alloys prepared by induction melting process at 1400℃and 1600℃are composed with Al, TiAl3, TiB2 and TiC phases. The TiB2 has plate-like shape with a length of 20μm, the TiC size spans from 2μm to submicron level, and the length of flake TiAl3 increased with the rising reaction temperature. The Al/B4C interface reaction, 3[Ti] + B4C =2TiB2 + TiC, is the key mechanism to generate TiB2 and TiC nucleating substrates.⑷The Al-Ti-B-C quaternary master alloys containing TiAl3, TiB2 and TiC had an excellent refining performance on commercial pure aluminum, compared with the master alloys only containing TiAl3. The mean grain sizes of commercial pure aluminum were diminished to 189μm and 192μm separately by adding 0.2wt% master alloys synthesized by induction melting process at 1400℃and 1600℃. After holding for 60 min, the diameter of commercial pure aluminum grain was stable around 220μm.⑸The combination effect of heterogeneous nucleation caused by TiB2 and TiC particles and the grain growth restriction caused by solute Ti is the main grain refinement mechanism of the quaternary Al-Ti-B-C master alloy. In the nucleating process,α-Al starts to form at the surface of TiB2 and TiC substrates which have a good wettability and lattice match with Al. In the later grain growth stage, the growth inhibition ofα-Al caused by solute Ti is the dominant effect. So, the refinement mechanism of Al-Ti-B-C mater alloy is a coupling effect of the carbon-boride theory and the solute theory.

Related Dissertations

  1. Correlation Study on T Cell Immunity, Related Psychosocial Factor and TD,R749.94
  2. Study on Relation between Behavior and Family Factors in Children with Tic Disorder,R749.94
  3. New Grain Refiners and Their Refining Behaviors of AZ31 Magnesium Alloy,TG146.22
  4. Effect of Adding ZrO 2 Nanopowder on Microstructure and Mechanical Properties of Carbon Steel,TB383.1
  5. The Affect of Microstructure and Properties Adding ZrO_ 2 Nanoparticles on Carbon Steel,TG142.31
  6. Supplemented by large deformation heat treatment asynchronous Roll Ultrafine twinned copper and its formation mechanism,TG166.2
  7. Magnetic field double wire submerged arc welding heat Numerical simulation and experimental study,TG445
  8. Wrought magnesium alloy microstructure and properties of thermomechanical treatment,TG146.22
  9. Ultrasonic deposition of spray forming blank Quality,TF124.39
  10. Variable Selection Methods Via the Elastic Net in Generalized Linear Models,O212.1
  11. 2124 aluminum alloy heat treatment on creep deformation aging effects,TG166.3
  12. Study Application of Warm-hot Extrusion Technique Information of Oxygen Lance Nozzle,TF124.3
  13. Study on Formation Mechanism and Mechanical Properties of Al2O3 -TiB2 Solid-state Reaction Multiphase Ceramic Coating,TG174.453
  14. The PQ600 high strength engineering machinery steel hot rolling process research,TG335.11
  15. Of TiC Reinforced relative Mo alloy mechanical properties and microstructure,TG146.412
  16. Process and mechanism of high strength aluminum alloy composite welding with ultrasonic agitation,TG453.9
  17. Technology and Mechanism on Argon Arc Welding of SiC Particle Reinforced 6061 Al Composites,TG444.74
  18. Study on Laser Welding of High Volume Fraction SiC_p/2024al Mmc with Ti Alloy Filler,TB331
  19. Research on Microstructure and Evolution of TiB2-Al2O3 Composite Ceramics Synthesyzed by SHS,TQ174.1
  20. Control Study on Characteristics of Attachment and Family in Children with Tic Disorders,R749.94
  21. Children with tic disorder syndromes Distribution and Related Factors,R272

CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Non - ferrous metals and their alloys > Light non-ferrous metals and their alloys > Aluminum
© 2012 www.DissertationTopic.Net  Mobile