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HPAM Paul 2 - Coggle Diagram

- - - - Angular, hard particles give ductile fracture
    - - No plastic deformation, it cracks :cry:
      - Rounded particles
  - - - Upon movement the asperity junctions are fractured leaving material stuck to the other
    - - At lower loads metal oxides interact
      - Metal-metal bonds are stronger than oxide-oxide bonds so mild wear and low loads
      - :arrow_up: load = severe wear from metal-metal contact = :arrow_up: temp and reformation of oxide reducing wear
- - - - High temp \(\beta\) has high diffusivity (diffusional creep dominates)
      - Ti alloys dissolve their own oxide leading to fires on rubbing
    - - Stengthening is limited by \(\alpha2\) formation (brittle intermetallic)
    - - Fe and Cr give a eutectoid that is rarely seen so treated as beta stabilisers
    - - Processed in \(\alpha\)phase field giving elongated grains and strong texturing
      - Processed in \(\beta\) phase field have Widmanstatten structure
    - - Stable \(\beta\)
        
        At least 25 wt % \(\beta\)
        
        Can be cold rolled to combat explosive grain growth
        
        High density
      - Metastable (Martensitic) \(\beta\)
        
        10wt% \(\beta\) stabilisers
        
        Slow cooling from \(\beta\) gives Widmanstatten
        
        Fast coolign gives \(\alpha' and \alpha''' \)(HCP, favoured by V) or \(\alpha''\) (orthorhombic, favoured by Mo)
        
        Soft and low volume change so less distortion or cracking
        
        Tempering (600C several hours), fine \(\alpha\) forms along prior \(\beta\) grain boundaries with scicular \(\alpha\) plates surrounded by retained \(\beta\)
        
        \(\alpha\) provides strengthening and \(\beta\) provides crack blunting
        
        \(\omega\) must be avoided on quenching and aging
      - \(\alpha + \beta\)
        
        Most common
        
        Forged and machined not cold deformed
        
        Avoid O-rich \(\alpha\) as :arrow_down: toughness and fatigue life
        
        Treating in the \(\alpha +\beta\) region gives primary \(\alpha\) that pins grain boundaries and gives finer prior \(\beta\) grain size
        
        On cooling \(\beta\) transforms to grain boundary \(\alpha\), widmanstatten/acicular \(\alpha\), martensite or is retained
        
        Treating in the \(\beta\) region gives no grain boundary pinning and very large prior \(\beta\) grain size
        
        On cooling, transforms to grain boundary \(\alpha\), widmanstatten/acicular \(\alpha\), martensite or is retained