Here is the explained answer :–

Step 1:– Phase diagram :– A phase diagram in physical chemistry, engineering, mineralogy, and materials science is a type of chart used to show conditions at which thermodynamically distinct phases occur and coexist at equilibrium.

Step 2 :– According to these diagrams :–

These can be useful to predict the percentage composition of alloying component at some instant using lever rule (explanation) :–

( i ) In chemistry, the lever rule is a formula used to determine the mole fraction (xi) or the mass fraction (wi) of each phase of a binary equilibrium phase diagram.

(ii) Lever rule is used to determine the relative amount of each phase in a mixture. It takes the help of a tie-line at a given temperature.

(iii) The two phases at a given temperature have two different compositions, but overall the amounts of these two compositions must add up to the alloy’s overall composition.

(iv) At a constitution point in a single-phase region, the phase composition is simply the composition of the alloy itself . In two-phase regions, the phase compositions are given by the values on the phase boundaries at the ends of the tie-line through the constitution point.

(v) Each region corresponds to the range of combinations of temperature and pressure over which that phase is stable. The combination of high pressure and low temperature (upper left )corresponds to the solid phase, whereas the gas phase is favored at high temperature and low pressure (lower right).

(vi) Phase diagrams are useful because they allow us to understand in what state matter exists under certain conditions.