Question

Question 3 (Total 17 marks)- °C 1100 Atomic percent silver 40 50 10 20 30 60 70 80 90 F 1084.5 1900 1000 L 900 1. + 961.93) 1700 1600 L+B 1400 91.2 800 a B 780° 7.9 71.9 700 1200 600 -- 1000 500 850 400 Cu 10 20 30 70 SO 90 Ag 40 SO 60 Weight percent silver Above is a phase diagram of Cu - Ag.- (a) Which phase(s) exist at 80%wt Ag, 20%wt Cu at 800°C (1 mark) (b) At what temperature does 40%wt Ag, 60%wt Cu completely melt (1 mark) (c) For 75%wt Ag 25%wt Cu at 700°C what is the composition of all the phases present (2 marks) (d) Using the Lever rule, determine the weight fractions of each phase for 75%wt Ag 25%wt Cu at 700°C (3 marks)

Answer 1

Solution Bon Hence (6) At 40 wt % Ag we @) at when we draw 80 wł % Ag and 20wt% Lee veedical line and at draw horizontal line then these two lines intersect at at point and that point lies in ßt2 region B-phase and L phase exist 60 wt%lu we will draw vertical line The point at which it intersects to the liquidus line will draw horizontal line This horizontal line will finally give its melting point Mence at around 910°C 40% tAg 160 wtrue will completely melt 75 wł 7. Ag and 25 wt% lee duan hourontal line at 700c it will the solvus line of Ag in u and soluus line of cu in Aq Solves line of Ag in u gives composition of a-phase .94 wt %lu) (9H Wt % Ag yo wt% ) rule (d) B. Phase 94 weight fraction of a-phase ita =94-75 we "Caround 6.2% Ag ß phase By lever a phase + 75 6 94-6 weight fraction 0.216 of B-phase ; fp = 75-6 94-6 = 0.784