(1)

A

Terminal solid solution $Al$ and $Li$
Intermediate solid solution $\beta$
Intermetallic compounds $Al_2Li_3$ amd $Al_4Li_9$

B

The solubility limit of Al in Li at temperatures below 150°C would be around 63.3wt% Al.

C

1 $L \trans Al + \beta$ liquid in equilibrium with two solids [Eutectic]
2 $L \trans \beta $ liquid in equilibrium with one solid [Isomorphous]
3 $L + \beta \trans Al_2Li_3 $ liquid and solid in equilibrium with one solid [Peritectic]

D

A $Al + \beta$
B $Al_2Li_3 + L$

E

$Al_4Li_9$$= \cfrac{\color{#0071BC}R}{{\color{#009245}S} + {\color{#0071BC}R}} = $ 63wt% (63.3wt% $Al$ and 36.7wt% $Li$)
$Li$$= \cfrac{\color{#009245}S}{{\color{#009245}S} + {\color{#0071BC}R}} = $ 37wt% (100wt% $Li$)

F

Aluminium can be precipitation strengthened using no more than ~4.6wt% lithium. In this region percipitation of the $\beta$ phase in Al can occur ($Al \trans Al + \beta$). Between 21wt% - 23.3wt% Li percipitation of $Al_2Li_3$ in $\beta$ can also occur ($\beta \trans Al_2Li_3 + \beta$).

(2)

A

$\alpha$Ferrite
$\gamma$Austenite
$\delta$High temperature BCC
$Fe_3C$Cementite
$L$Liquid

B

Martensite is an unstable phase and does not exist in equilibrium. Martensitic phase transformation occurs from rapid quenching. As the phase diagram above only shows the phases in equilibrium, martensite does not present itself.

C

Microconstituent Phases Present Microstructure
Martensite Body-centered tetragonal, single phase Needle like grains.
Tempered Martensite $\alpha$ + $Fe_3C$ Very fine round particles of $Fe_3C$ in an $\alpha$ matrix.
Bainite $\alpha$ + $Fe_3C$ Fine rod like particles of $Fe_3C$ in an $\alpha$ matrix.
Fine Pearlite $\alpha$ + $Fe_3C$ Alternating relatively thin layers of $\alpha$ and $Fe_3C$.
Coarse Pearlite $\alpha$ + $Fe_3C$ Alternating relatively thick layers of $\alpha$ and $Fe_3C$.
Spheroidite $\alpha$ + $Fe_3C$ Relatively large particles of $Fe_3C$ in a $\alpha$ matrix.
Assuming eutectic steel composition

(3)

A

Pearlite formed at higher temperature (less supercooling) will form coarser perlite as more atomic diffusion can occur and larger grains will from. With lower supercooling the stable nuclie size will be larger and there will be fewer nuclie formed (coarse). With higher supercooling the stable nuclie size will be smaller and hence more nuclie formed (finner).

B

By quenching, the material has no time for atomic diffusion to occur. This forces the BCC structure of the austenite to destort into the BCT structure of martensite, due to the reduction in atomic spacing from rapid decrease in temperature.

C

Martensite is highly brittle due to fewer slip systems and interstitial carbon atoms. Tempering martensite produces extreamly small cermentite particales surrounded by ferrite. By tempering martensite we allow for atomic diffusion to occur and the energy of the system can be reduced, making a less brittle material.

(4)

Stress Relief Reduces stresses caused from plastic deformation, nonuniform cooling and phase transformations.
Process Anneal Negates the effects of cold work (by recovery/recrystallization) makes the material less brittle.
Spheroidize Makes steel very soft and good for machining (constant heat just bellow $T_E$ for 15-25hrs).
Full Anneal Creates a course perlite structure, making steel softer and good for forming (slow cooling in furnace).
Normalize Makes steel stronger by reducing grain size (fast cooling in air).

(5)

Solution-treated, the samples were heated to 500˚C for 5hrs creating a metal solution. The solution was then quenched in liquid nitrogen (LN), retaining the solutions structure. This solution treatment process created a coarse grained solid solution resulting in a higher ductility and weaker strength. By cryogenically rolling the samples a high density of dislocation where created and the grain size was reduced significantly. This cold work process made the material brittle and stronger. An aging process was then used to form percipitants. High dislocation density created from cold work resulted in lots of small percipitants. This percipitation hardening process made the material stronger and more ductile through dislocation accumulation. The unique processing strategy is effective by combination of three metal processing techniques to obtain a microstructre within the alloy that improved it's strength whilst retaining good ductility.