MEEN_360_Quiz_5_AB

What is the critical value of G to avoid constitutional supercooling for the directional solidification of an Al-Cu alloy, containing 3 wt.% copper, at a rate of 0.05 mm/s? For these alloys, k = 0.14, m = -2.6oC/wt% and D = 3x10-5 cm 2 /s. Here G is the thermal gradient into the liquid phase, k is the partition coefficient of the alloy, and D is the diffusivity of solute in the liquid phase.

Select all that apply. Which parameters are going to affect the ease at which a solid state diffusional phase transformation will nucleaate? Interphase surface energy Undercooling or supercooling Enthalpy of transformation Volume difference between the two phases

Q) A graph of your temperature versus time cooling curve. Discuss the indicators of solidification initiation and termination and the implied alloy composition(s) I have provided with the grpah of the tmep vs time cooling curve and the phase diagram please answer the above question accordingly in paragrahps

Briefly explain the heat treatment processing techniques using a phase diagram.

Answer part b

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Draw two different types of temperature-composition phase diagrams for an exemplary liquid-solid system, show the important regions and explain the leverage rule on the diagram by deriving the relevant relations.

1 a) Briefly describe the phenomenon of coring (also known as segregation) that occurs during solidification in isomorphous alloys and why it occurs? b) Cite one undesirable consequence of coring?

b) For the solidification of a metal, Tm =1000K with undercooling of 200K, calculate the rate of homogeneous nucleation in nuclei/m³/s. Neglect activation energy. Assume v=1o12/s and s'pd estimated as 1028/m³, AH=-1.26x10° J/m³, yLs= 0.16 J/m².

Choose the correct graph

Visualize a substance with the following points on the phase diagram: a triple point at 0.05 atm and 150 K; a normal melting point at 175 K; A normal boiling at 350 K; and a Critical point at 2.0 atm and 450 K. The solid liquid line is normal. For this complete the following:  a. Describe what one would see at pressures and temperatures above 2.0 atm and 450 K. b. Describe the phase changes from 50 K to 250 K at 1.5 atm

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What is the critical value of G for the directional solidification of two Al-Cu alloys (one containing 3wt.%Cu, the other 5wt.%Cu) at a rate of 0.08 mm/s ? For these alloys, k=0.14, m=-2.6°C/wt% and D=3x10-5cm²/s.

(a) Figure 5 shows a phase diagram for the Nb-80 wt% W alloy which is solidified under under the nonequilibrium condition. Evaluate (i) the liquidus temperature (ii) the non-equilibrium solidus temperature (iii) the freezing range (iv) the composition of the first solid form during solidification (v) the composition of the last liquid to solidify (vi) the phase(s) present, the composition of the phase(s) and the amount of the phase(s) at 3000 °C (vii) the phase(s) present, the composition of the phase(s) and the amount of the phase(s) at 2800 °C.

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Draw a PVT surface and indicate the regions where two phases coexist and label the axes

Please answer all of the parts from a to e

1.50% Pearlite, 50% Tempered Martensite 2.50% Bainite, 45% Martensite, 5% Austenite

Please use phase diagram to explain why micro-segregation and macro-segregation happen during practical solidification.

KS) A binary alloy having 28 wt% Cu and balance Ag solidifies at 779°C. The solid consists of two phases a and B. Phase a has 9% Cu whereas phase ß has 8 % Ag at 779°C. At room temperature these are pure Ag and Cu respectively Sketch the phase diagram. Label all phases and temperatures. The melting points of copper and silver are 1083° and 96100 respectively us? Estimate the amount of a and B in the above alloy at 779°C and at room temperature.) b) Calculate the mass fraction of phases for 40% Cu alloy at 300 °C and TR c) What is the composition of the alloys in (b) following:

Phase Diagrams Question-1 (a) What is a binary isomorphous alloy system? (b) What are the four Hume-Rothery rules for the solid solubility of one element in another? (c) Describe how the liquidus and solidus of a binary isomorphous phase diagram can be determined experimentally. (d) Explain how a cored structure is produced in a 70% Cu-30% Ni alloy. How can the cored structure be eliminated by heat treatment?

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From the phase diagram of the Fe-0.25wt%C alloy below, determine the phase fraction and elemental composition of the resulting phase immediately after solidification across the eutectoid line (725 C). a.alpha_eutectoid = 96.6 wt% and cementite = 29.85 wt% b.alpha_eutectoid = 96.6 wt% and cementite = 3.4 wt% c.alpha_eutectoid = 1.05 wt% and cementite = 29.85 wt% d.alpha_eutectoid = 29.85 wt% and cementite = 1.05 wt%

Q. Solidification patterns of steel, with different composition of carbon, in sand and metal molds by time elapse are represented in the following images. Briefly explain the differences observed between the microstructure that develop from mold walls in each case.

6. Figure shows the cooling curve for aNiO-MgO ceramic. (f) the local solidification time; 2800 2700 2600 2525 2500 28 2400 10 20 30 40 50 Time (min) Temperature (°C)

13. For the heterogeneous solidification, derive the critical radius of solid nucleus r*, the activation free energy of nucleation AG*, and the number of stable nuclei n*.

Provide a hypothetical procedure for measuring the phase diagram at different temperatures.

Discuss the solid solution hardening mechanism

An AL disk with a diameter = 10 cm and thickness = 5 cm is cast of pure aluminum in asand casting operation. Aluminum melts at 660C, but the pouring temperature will be800C. The heat of fusion of aluminum = 398 J/g. Assume the specific heat has the samevalue for solid and molten aluminum. C = 0.23 Cal/gC= 0.879 J/gCCompute. a. the unit energy for melting and pouring.b. the total energy to heat the metal to the pouring temperature starting from a roomtemperature of 25C.