Investigation and Optimization of Ti-6Al-4V Alloy ... Optimisation of Fatigue Behaviour of Ti-6Al-4V

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Text of Investigation and Optimization of Ti-6Al-4V Alloy ... Optimisation of Fatigue Behaviour of Ti-6Al-4V

  • Optimisation of Fatigue Behaviour of

    Ti-6Al-4V Alloy Components

    Fabricated by Metal Injection Moulding

    Vom Promotionsausschuss der

    Technischen Universität Hamburg-Harburg

    zur Erlangung des akademischen Grades

    Doktor Ingenieur (Dr.-Ing.)

    genehmigte Dissertation

    von

    Orley Milagres Ferri

    aus

    Belo Horizonte, Brasil

    2010

  • Vorsitzender des Prüfungsausschusses: Prof. Dr.re.nat. G. Schneider

    1. Gutachter: Prof. Dr.-Ing. R. Bormann

    2. Gutachter: Prof. Dr.-Ing. J. Albrecht

    3. Gutachter: Prof. Dr.-Ing. K.U. Kainer

    Tag der mündlichen Prüfung: 29 Oktober 2010

  • Acknowledgments

    Many people contributed to my doctoral thesis over the last three years. Especially, I

    would like to thank …

    ... my advisor, Prof. Rüdiger Bormann, for giving me the opportunity to

    work on this exciting topic, as well as for his guidance, support and

    motivation.

    ... my co-advisor, Dr. Thomas Ebel, for the excellent orientation and

    discussions along experimental and written steps of my doctoral thesis.

    ... Prof. J. Albrecht and Prof. K.U. Kainer for co-reviewing the thesis.

    ... present members of the research group of WZM at GKSS: Wolfgang

    Limberg, Martin Wolff, Andreas Dobernowsky, Prof. M. Dahms and

    Gitta Hillis.

    ... all former students who worked on term, diploma or master thesis:

    Juliano Soyama, Gideon Obasi, Akaichi Haithem, Björn Wiese, Arno

    Twardogorski and Sascha Fensky.

    ... all former students who worked on term of DAAD rise program: Alyson

    Liser and William Andrew Sharp II.

    ... my wife Lígia for her love, unfailing support and encouragement.

    Geesthacht, Oktober 2010

  • CONTENTS

    i

    1. Introduction .................................................................................................................. 1

    1.1. Scope of the work .................................................................................................. 2

    2. State of the art ............................................................................................................... 3

    2.1. Ti-6Al-4V alloy ..................................................................................................... 3

    2.2. Metal injection moulding process.......................................................................... 6

    2.2.1. Powders for MIM ........................................................................................... 7

    2.2.2. Binder for MIM .............................................................................................. 7

    2.2.3. Injection moulding and debinding .................................................................. 8

    2.2.4. Sintering ....................................................................................................... 10

    2.3. MIM of Ti-6Al-4V alloy ..................................................................................... 13

    2.4. Fatigue ................................................................................................................. 14

    2.4.1. Fatigue in Ti-6Al-4V alloy ........................................................................... 17

    3. Experimental procedures ............................................................................................ 20

    3.1. Materials .............................................................................................................. 20

    3.2. MIM process ........................................................................................................ 20

    3.2.1. Binder content .............................................................................................. 22

    3.2.2. Particle size ................................................................................................... 23

    3.2.3. Boron addition .............................................................................................. 23

    3.3. The hot isostatic pressing .................................................................................... 24

    3.3.1. Powder+HIP ................................................................................................. 24

    3.3.2. MIM+HIP ..................................................................................................... 25

    3.4. Surface modification and characterisation .......................................................... 25

    3.5. Characterization of the samples ........................................................................... 26

    3.5.1. Impurity levels, microstructural features and relative density ..................... 26

    3.5.2. EBSD measurements .................................................................................... 28

    3.5.3. Dilatometry ................................................................................................... 28

    3.5.4. Tensile test .................................................................................................... 29

    3.5.5. Fatigue experiments ...................................................................................... 30

    4. Verification of the four-point bending fatigue tests ................................................... 32

    4.1. Experimental procedure ....................................................................................... 32

    4.2. Results and discussion ......................................................................................... 32

    5. Results ........................................................................................................................ 35

  • CONTENTS

    ii

    5.1. The MIM31L samples ......................................................................................... 35

    5.1.1. Tensile mechanical behaviour ...................................................................... 36

    5.1.2. Fatigue behaviour ......................................................................................... 37

    5.2. Binder content...................................................................................................... 41

    5.2.1. Microstructural features ................................................................................ 41

    5.2.2. Tensile properties ......................................................................................... 44

    5.2.3. Fatigue behaviour ......................................................................................... 46

    5.3. Shot peening as a surface treatment .................................................................... 48

    5.3.1. Fatigue behaviour ......................................................................................... 48

    5.3.2. The internal stresses promoted by the shot peening ..................................... 52

    5.4. Particle size .......................................................................................................... 55

    5.4.1. Microstructural features and tensile properties ............................................ 55

    5.4.2. Fatigue behaviour ......................................................................................... 57

    5.5. The MIM+HIP configuration .............................................................................. 59

    5.5.1. Microstructural features ................................................................................ 59

    5.5.2. Tensile properties ......................................................................................... 60

    5.5.3. Fatigue behaviour ......................................................................................... 61

    5.6. The Powder+HIP configuration........................................................................... 64

    5.6.1. Microstructural features ................................................................................ 64

    5.6.2. Tensile properties ......................................................................................... 66

    5.6.3. Fatigue behaviour ......................................................................................... 67

    5.7. Addition of boron on Ti-6Al-4V alloy ................................................................ 70

    5.7.1. Boron content ............................................................................................... 70

    5.7.2. Dilatometry ................................................................................................... 72

    5.7.3. Impurity levels and microstructural features ................................................ 74

    5.7.4. Tensile properties of the Ti-6Al-4V-0.5B alloy ........................................... 79

    5.7.5. Fatigue behaviour ......................................................................................... 80

    6. Discussion ................................................................................................................... 84

    6.1. The influence of interstitial elements on the mechanical properties of MIM

    samples ....................................................................................................................... 84

    6.2. Ti-6Al-4V alloy processed by MIM ............