The following data apply to the binary system of A and B:                                                                                                                                                     Melting point of pure A = 1050°C                                                                                                                                                                                                       Melting point of pure B = 1900°C

At 1250°C, the α solid solution (containing 50% of B), the β  solid solution (containing 80% of B) and liquid (containing 30% of B) are in three-phase equilibrium. At room temperature, the maximum solubility of B in the α  phase is 30% and the maximum solubility of A in the β  phase is 10%.

(i) Sketch the phase diagram of A and B, showing the phases present in each area of the diagram.

(ii) What is the reaction that takes place at 1250°?

(iii) What are the weight fractions of the phases present in a material of overall composition 75% B, at 1251°C, 1249°C and at room temperature (RT)?