notes on diffusion, deformation processes

uni/mmme/1029_materials_and_manufacturing/manufacturing.md

@@ -131,3 +131,50 @@ $$C = \frac{mC_m}{1-f} + \frac{C_t}{n} + \frac{1}{\dot n} \left[ \dot C_{oh} + \
 - Low thermal capacity and high conductibity
 - Low solubility
 - Not contaminated by air
+
+## Deformation
+
+When a metal is plastically deformed, dislocations move and multiply.
+
+Annealed aluminium may have a dislocatio density of around 200 m per mm$^3$.
+This is a very low amount.
+A heavily cold worked piece may have a density of up to 270 km per mm$^3$.
+
+As dislocation density increases, the dislocations impede the motion of other dislocations.
+This means that to continue plastically deforming, more stress has to be applied.
+
+The stress goes down towards the end of the graph due to the material necking, meaning the
+material gets thinner.
+This means that the engineering stress is lower as the true area is lower.
+The true stress, however, is going up:
+
+![](./images/vimscrot-2022-02-28T20:01:59,453437307+00:00.png)
+
+### Effect of Prior Deformation (*Work Hardening*)
+
+![](./images/vimscrot-2022-02-28T20:02:42,050513187+00:00.png)
+
+See
+[here](materials.html#work-hardening-and-cold-working)
+for more information
+
+### Effect of Temperature (Diffusion)
+
+In an alloy, atoms tend to migrate from regions of high concentration to low concentration.
+This is diffusion.
+
+More information on diffusion [here](materials.html#diffusion).
+
+### Annealing
+
+Annealing is a process by which a component is heated to reduce work hardening.
+
+![](./images/vimscrot-2022-02-28T20:32:47,838820599+00:00.png)
+
+These are diffusional processes and only occur at higher temperatures.
+
+When the temperature of a material, $T > 0.55T_m$, it is said to be hot.
+A material being worked on hot has its deformations eliminated as fast as they are created.
+
+A material is said to be cold when $T < 0.35T_m$.
+