Segregation of phosphorus to ferrite grain boundaries during transformation in an Fe-P alloy

A binary alloy of iron containing 0.17 wt.% of phosphorus has been heat treated under a variety of conditions in order to see whether the segregation of phosphorus to grain boundaries can be controlled. The alloy transforms fully into ferrite. It is found that the majority of solute found at the ferrite grain boundaries has its origins in the temperature range where phase transformation occurs, in other words, phosphorus that is accumulated and dragged with the growing ferrite-austenite transformation front. As a consequence, it cannot be suppressed using cooling rates as high as 400 K s(-1).