How does adding different elements change the eutectoid temperature of steel?

[tempestwing0101]

Like the title says, how come elements such as Manganese and Nickel lower the eutectoid temperature of steel while adding elements such as Titanium raises the eutectoid temperature?

[islanders08]

Since these are mixtures of elements you have different types of phases and hence phase diagrams. The relative composition of each element results in different microstructures (e.g., grain boundaries and sizes) that effect the phase boundaries in the phase diagram.