A binary phase diagram of components P and Q displays an eutectoid reaction with terminal solid solutions a on the P rich side and β on the Q rich side. At the eutectoid temperature, the solubilities of Q in a and β are 5 and 90 wt% respectively. The densities of α and β phases are 9.5 and 2.49 gm/cm³ respectively.
At the eutectoid point, the alloy has α and β in the weight ratio 1 : 1. The eutectoid point occurs at composition . . . . . . . . wt % Q.