Problem Two ${?}^{[30\text{M}\text{a}\text{r}\text{k}\text{s}]}$

Specify the nature of the final microstructure $($in terms of microconstituents present with approximate

percentages, and phases with proportions$)$ and estimate the Brinell Hardness and Ductility $(\%$RA$)$ of a small

Eutectoid Steel specimen that has been subjected to the following time$-$temperature treatments. In each case,

assume that the specimen begins at $760C$ and that it has been held at this temperature long enough to have

achieved a complete and homogeneous austenitic structure.

$($A$)$ Rapidly cool to $400C,$ hold for ${10}^{3}s,$ then quench to room temperature.

$($B$)$ Rapidly cool to $650C,$ hold for $10$ s $,$ then quench to room temperature.

$($C$)$ Rapidly cool to $600C,$ hold for $4$ s $,$ rapidly cool to $450C,$ hold for $10$ s $,$ then quench to room temperature.

$($D$)$ Rapidly cool to $600C,$ hold for $4$ s $,$ rapidly cool to $450C,$ hold for $10$ s $,$ then quench to room temperature.

Reheat to $700C$ for $20$ h $.$

$($E$)$ Rapidly cool to $300C,$ hold for $20$ s $,$ then quench to room temperature in water. Reheat to $425C,$ for ${10}^{4}s$

and slowly cool to room temperature. $($Note: You do not need to determine the Ductility$)$

$($F$)$ Rapidly cool to $400C,$ hold for $150$ s $,$ then quench to room temperature.