add notes on heat treatments

uni/mmme/1029_materials_and_manufacturing/materials.md

@@ -1090,7 +1090,7 @@ As you decrease grain size, you get more grain boundaries which basically create
 to prevent slip.
 
 This is because a dislocation would have to change orientation across a grain boundary and "ionic
-disorder in the grain boundary results in discontinuity of slip" (A.B Seddon University of
+disorder in the grain boundary results in discontinuity of slip" (A.B Seddon, University of
 Nottingham 2020) (I think that's repeating it but it said it on the slideshow sooo...).
 
 So for any given metal, the fine grained is harder and has greater yield stress than the coarse
@@ -1104,6 +1104,41 @@ where $d$ is the grain size and $\sigma_0$ and $k_y$ are material constants.
 
 Therefore a plot of $\sigma_{yield}$ against $d^{-0.5}$ would results in a straight line.
 
+## Heat Treatment of Metals
+
+These processes are to change a material's mechanical properties, not change its shape.
+
+### Phase Diagrams
+
+Here is an example of a *two component phase diagram* with a familiar system:
+
+![](./images/vimscrot-2022-03-07T14:16:57,570858805+00:00.png)
+
+The component in this case are sugar and water, but not syrup.
+
+A *phase* is a chemically and physically distinct species as we can have a change in phase that goes
+from solid to solid.
+
+The *solubility limit* is the maximum concentration for which only a solution occurs.
+In the case of this system, thee limit increases with temperature.
+
+Here is a generic phase diagram for a generic *A-B* system:
+
+![](./images/vimscrot-2022-03-07T14:26:08,092894184+00:00.png)
+
+- L - liquid
+- $\alpha$ --- a solid phase but still a solution. B can dissolve into A
+- $\beta$ --- a solid phase but still a solution. A can dissolve into B
+
+### Annealing
+
+Annealing is a process by which a component is heated to remove the effects of cold work.
+
+![](./images/vimscrot-2022-03-07T14:15:01,296649522+00:00.png)
+
+These are diffusional processes and only occur at high temperatures.
+The driver for diffusion is the removal of high energy defects from the system.
+
 # Diffusion
 
 Diffusion is atomic or ionic movement down a concentration gradient.