Dissertation > Excellent graduate degree dissertation topics show

Research on Technology of TIG Arc Welding Brazing and Interfacial Characteristic of Ti/al Dissimilar Alloys

Author: JingXiaoJun
Tutor: LvShiXiong
School: Harbin Institute of Technology
Course: Materials Engineering
Keywords: Ti/Al dissimilar alloys arc welding brazing spreadability interfaciallayer alloying element
CLC: TG454
Type: Master's thesis
Year: 2012
Downloads: 25
Quote: 0
Read: Download Dissertation

Abstract


Titanium reacts with aluminum to form brittle intermetallic compounds (IMCs)due to their incompatible metallurgical weldability. So joining of Ti/Al hybridstructures has always been one of the hot research topics for welding workers.Nowadays, arc welding-brazing, which has advantages on equipment costs andapplied scopes, is gradually concerned. However, two major problems, including thepoor spreadability of filler metal on Ti substrates with TIG heating and formation ofvast IMCs at the interface, retard its research and application on joining of Ti/Alhybrid structures. Therefore, illustration on the filler’s spreadability on the Tisurfaces with arc heating and the growth of interfacial reaction layer is the most keyfactor to obtain a sound Ti/Al welding-brazed joint.This paper has developed systemic research on butt joining of Ti/Al dissimilaralloys with arc welding-brazing technique. Firstly, a novel technique, referred to asthe keyhole arc welding-brazing (K-AWB), was presented based on the analysis oftemperature field by the finite element methods and filler’s spreading experiments.And the temperature distribution of Ti/Al butt joints and spreadability of fillers onTi surfaces were clarified. A good weld forming of joints was achieved by adjustingthe heat input, heating location and filler patterns. Then, microstructures ofwelding-brazed joints were observed and the mechanical properties of the jointswere evaluated by tensile and hardness tests. Based on the analysis ofmicrostructures and fracture characteristics, the failure mechanism of the joints andits impact factors were revealed. At last, the research was focused on the growthregulation of Ti/Al interfacial reaction layer, and thermodynamical analysis, kineticmethod and experimental research were conducted.The results showed that the weld pool exhibited dynamic circular stages,including elliptic pool, breached pool, keyhole pool and elliptic pool, when a lowwelding speed and pulsing feeding of fillers were adopted. The liquid filler spreadwell on all the joint surfaces, single face welding-double face forming of Ti/Al buttjoints were easily achieved by the K-AWB technique. A serrated layer with athickness of4-6μm was observed at the interface with pure Al filler and theinterfacial structure is Ti(Al)+Ti3Al+TiAl3multilayers, which uniformly distributedat the joints’ thickness direction. With adding of Al-Cu-La filler, Ti2Al20La phasewas produced at the interface near the Al side and tensile strength of the jointreached270MPa. Investigation on thermodynamical and kinetic characteristicsconcluded that TiAl3phase first formed, compared to the other Ti-Al IMCs and the reaction to form TiAl3only occurred at the cooling stage of the welding brazingprocess. The growth of layer included spreading and absorption of liquid filler on Tisubstrate, heterogeneous diffusion of Ti and Al, phase transformation to form Ti3Aland nucleation and growth of TiAl3layer. The thicknesses and morphologies ofinterfacial layers varied dramatically with the increase of heat input. Nucleation ofTiAl3was boosted and a relax-shaped TiAl3layer was observed with the help of La,Zr and B elements. The Ti2Al20La phase formed along the TiAl3interface, while the(Ti,Zr)Al3grew up on the base of TiAl3. TiB2and AlB12particles were detected inthe interfacial layer with B element added. With the adding of Si element in thefiller metal, though the thickness of the layer was increased, the interfacial structurewas also changed and a good bonding was obtained.

Related Dissertations

  1. TiH2 Decomposition Kinetics and Preparation of Aluminum Foam Reinforced by Copper-coated Carbon Fibers,TB383.4
  2. The Design and Research on a Gas-water Mix-type Marine Fire Hydrant,U664.88
  3. Research on Brazing CBN Grains with Ag-Cu-Ti Filler Reinforced by TiN Particles,TG454
  4. Add trace elements on Sn-0.7Cu lead-free solder performance,TG425
  5. Investigation on the Electrochemical Properties of Amorphous La-Mg-Ni System Hydrogen Storage Alloys,TG139.7
  6. Composition Design and Preparation of Heat-Resisting Hyper-Eutectic Al-Si Alloy,TG146.21
  7. Study on As-Cast Mg-Zn-Al-Ca Heat-resistant Magnesium Alloy,TG27
  8. The Effect of Alloying Elements on the Microstructure and Mechanical Property of Al-Si-Cu-Mg Cast Alloy,TG113
  9. Microstructure and Mechanical Properties of Die Cast Magnesium Alloy Mg-Zn-Al-Ca,TG113
  10. Morphology and Controlling of the Second Phase in the Wear-Resistant AlSiFe Alloy,TG115
  11. Study on Changing Character of Cast Iron and Cast Steel under Pressure,TG250
  12. Effects of Ga/In and Rare Earth Ce on Microstructures and Properties of Brazed Joint of Ag30CuZnSn Filler Metal,TG425
  13. The dissolution behavior and mechanism of the aluminum anode in chloride solutions,O614.31
  14. Study on Semi-Solid Forming Process of Al-Si-Fe Alloy,TF807
  15. Study on RefiningTechnology and Mechanism of Cast Stainless Steel,TF769
  16. The Study on Microstructure and Mechanical Property of High Performance Hypoeutectic Casting Al-Si Alloy,TG146.21
  17. The Study on Hydrogen and Inclusion in Alumium Melt,TG146.21
  18. Influences of Alloying Elements on Microstructures and Properties of Brazed-Fusion Welded Joint of Aluminum Alloy to Steel Plate,TG407
  19. Effect and Mechanism of Al and Ag on Zn-Al Filler Metal,TG425
  20. Micro-scaled Chemical Reactions and Material Synthesis Modified by High-energy Laser,TB383.1
  21. The Isothermal Sections of the Mn-Si-TM(TM=Ni,Zr,Ti)Ternary System at600℃,TG113.14

CLC: > Industrial Technology > Metallurgy and Metal Craft > Welding, metal cutting and metal bonding > Welding process > Brazing
© 2012 www.DissertationTopic.Net  Mobile