Solution Found!
The temperaturecomposition diagram for the Ca/Si binary system is shown in Fig. 6.46
Chapter 6, Problem 6.9(choose chapter or problem)
The temperature composition diagram for the Ca/Si binary system is shown in Fig. 6.46. (a) Identify eutectics, congruent melting compounds, and incongruent melting compounds. (b) If a 20 percent by atom composition melt of silicon at \(1500^{\circ} \mathrm{C}\) is cooled to \(1000^{\circ} \mathrm{C}\), what phases (and phase composition) would be at equilibrium? Estimate the relative amounts of each phase. (c) Describe the equilibrium phases observed when an 80 percent by atom composition Si melt is cooled to \(1030^{\circ} \mathrm{C}\). What phases, and relative amounts, would be at equilibrium at a temperature (i) slightly higher than \(1030^{\circ} \mathrm{C}\), (ii) slightly lower than \(1030^{\circ} \mathrm{C}\)? Draw a graph of the mole percentages of both Si(s) and \(\mathrm{CaSi}_{2}(\mathrm{~s})\) as a function of mole percentage of melt that is freezing at \(1030^{\circ} \mathrm{C}\).
Questions & Answers
QUESTION:
The temperature composition diagram for the Ca/Si binary system is shown in Fig. 6.46. (a) Identify eutectics, congruent melting compounds, and incongruent melting compounds. (b) If a 20 percent by atom composition melt of silicon at \(1500^{\circ} \mathrm{C}\) is cooled to \(1000^{\circ} \mathrm{C}\), what phases (and phase composition) would be at equilibrium? Estimate the relative amounts of each phase. (c) Describe the equilibrium phases observed when an 80 percent by atom composition Si melt is cooled to \(1030^{\circ} \mathrm{C}\). What phases, and relative amounts, would be at equilibrium at a temperature (i) slightly higher than \(1030^{\circ} \mathrm{C}\), (ii) slightly lower than \(1030^{\circ} \mathrm{C}\)? Draw a graph of the mole percentages of both Si(s) and \(\mathrm{CaSi}_{2}(\mathrm{~s})\) as a function of mole percentage of melt that is freezing at \(1030^{\circ} \mathrm{C}\).
ANSWER:Step 1 of 3
a)
The temperature composition diagram of Ca/Si is given.
Eutectic: 40.2 at % Si at \(1268^{\circ} \mathrm{C}\), Eutectic: 69.4 at % Si at \(1030^{\circ} \mathrm{C}\).
Eutectic: 69.4 at % Si at \(1030^{\circ} \mathrm{C}\).
Congruent melting compounds:
\(\begin{array}{l}\mathrm{Ca}_2\mathrm{Si}\mathrm{\ mp}=1314^{\circ}\mathrm{C}\\ \mathrm{CaSi\ }\mathrm{mp}=1324^{\circ}\mathrm{C}\end{array}\)
Incongruent melting compound:
\(\mathrm{CaSi}_2\mathrm{\ mp}=1040^{\circ}\mathrm{C}\) melts into CaSi(s) and liquid 68 at % Si).