Question

(4 marks) b) Precipitation hardening is the heat treatment to enhance strength and hardness of some metal alloy. Explain its process by showing their temperature difference for each process. (6 marks)

Answer 1

Precipitation hardening is the hardening of a material due to the growth of precipitates that impede dislocation motion.

Basically, this process involves heating a mixture to a high temperature, then cooling, then heating to a medium temperature, and finally cooling again. Here's a more detailed overview of the precipitation-hardening process:

1. Bring a mixture of two or more components to an elevated temperature, where they mix completely.
2. Cool the material very quickly to lock in the completely mixed state.
3. Bring the material to an intermediate temperature, often called the 'aging temperature'. The aging temperature must be high enough that diffusion can occur rapidly, but low enough that one of the components can no longer dissolve the other so that precipitation occurs.
4. Cool the material to room temperature after the precipitates have grown to the desired size. Since room temperature is too cool for diffusion to occur rapidly, the precipitates will stop growing.
   temperature time