Problem #$1$

Shown below is the time$-$temperature transformation diagram for a certain composition of steel.

In addition, the phase diagram of steel is shown for reference.

a$.$ Estimate the composition of this steel sample.

b$.$ Determine the microstructure of this sample that has the following heat treatment: $(1)$ heat to $900^($@$)$C for a long time, $(2)$ rapidly cool to $500^($@$)$C and hold for $2$ seconds, $(3)$ rapidly cool to $300^($@$)$C and hold for $10$ seconds, and $(4)$ rapidly cool to room temperature.

c$.$ What will occur if the sample from Part b is held for $1$ day at $500^($@$)$C for one day and then cooled to room temperature?

d$.$ Determine the microstructure of this sample that has the following heat treatment: $(1)$ heat to $900^($@$)$C for a long time, $(2)$ rapidly cool to $800^($@$)$C and hold for $1$ minute, and $(3)$ rapidly cool to room temperature.