Question

4. Nickel has normal free energy (surface tension) of 2.69 /m2 s a normal melting point of 1455 "C, enthalpy of fusion of +17.47 kJ/m, and surface a. Calculate the critical radius of nickel (in nm) at 1000 C. (2p) 2(2(28k) (17.47 : 117 XOA b. Assunning ΔGTisnegative, whatdoes negativeAhmeanfortheformation ofstablenucles? Explain. (Ip) 5. Utilizing the lead-tin phase diagram: For a 60 wr% Sn-40 wt% Pb alloy at 150 °C: a. What phase(s) is (are present? (Ip) 2 piases Present ( bc & β) b. Utilizing the Lever Rule: what are the wt % of the phases? (1) 6o3 14-10 c. What are the compositions of the phases? (2p) 99%, Sn For full credit: Write formula and show your work for full credit. 1. Write the "Phase Rule" for a two-component system and name each term in the rule. (2p) de d しu,.btr 乀> 2. What does F 0 mean (represent) in a one-component system. Discuss in terms of the stable phase(s) that may co-exist and the number of independent variables that can be changed. Hint: Draw schematic P vs. T for illustration. (2p) onet syste 3. Define in short sentences: (2p) a. Ductility b. Critical radius. minimum sze nvles into a sngle caysteul c. Activation free energy in nucleation. minnum energy required to Sten ㄴ nucle ahu d. Eutectoid point (write reaction). Soliol mihne of 2 Soldcs (Sol d (2p) dCalculate the densities of all phases. Ilie Asume total mass of 100 g ofcach uo 9 :.20 lc -23 S n 7m (10 +.13) ίου เ๐.uy /거 6, For a spherical mcleus ofradíus r: Δ0ne4%r'AG+4mry a. Rewrite ΔG for a cubic nucleus ofcdge length (lp) b. Derive an expression for a where a* is the critical cube edpe length (2p) 7.Cu-Ni alloy is 700 g Cu and 350 g Ni. Estimatc the ductility of the alloy. 2p) EL: 35 %EL

Answer 1

b) A negative gibbs energy signifies the reaction is spontaneous and the nucleus is stable thus it will fuse and solidify.

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