pa6_Oct20_09b - at the face centres Count the atoms in a...

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AERO3700 PA 6 Questions Only Tuesday, October 20 Purpose: Familiarization and review of Mg, superalloys and specialty steels Attendance will be taken – be sure to show the TA your AERO3700 work. Course Pack AERO3700 p 107: 13.15, 13.20, 13.21 Callister: 11D1 A . The key solutes in Ni-based superalloys are Al and/or Ti with a total of less than about 10 w/o. This creates a 2-phase equilibrium structure of γ and γ΄ . Using your notes, sketch the portion of Al-Ni-Ti ternary phase diagram that shows the regions of γ , γ + γ΄ , and γ΄ 1. γ has a random substitution solid solution FCC structure of Al and Ni. Sketch a single unit cell and count the atoms present. 2. Discuss how γ provides strength. 3. γ΄ is more complicated. It has a cubic lattice with Al (or Ti) at the corners and Ni
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Unformatted text preview: at the face centres. Count the atoms in a single unit cell and show that γ΄ is Ni 3 Al (or Ni3Ti). 4. Discuss how γ΄ provides strength. 5. γ΄΄ is more even more complicated. It appears when Nb is added and an ordered arrangement of Ni and Nb appears. It is based on a BCT (with c approx. 0.742 nm and a approx .362 nm) arrangement with Nb at the unit cell corners and in the body centre. Ni is at the top and bottom face centres, at the vertical midedges and in 2 places on each vertical face. Count the atoms in a single unit cell and show that γ΄΄ is Ni 3 Nb. 6. Discuss how γ΄΄ adds strength. M. McDill AERO3700...
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