UNIVERSITI TEKNIKAL MALAYSIA MELAKA

FAKULTI KEJURUTERAAN MEKANIKAL

BMCB 2423 – MATERIAL SCIENCETUTORIAL 6

MATERIALS SCIENCE AND ENGINEERING

Q1. Define (a) a phase in a material and (b) a phase diagram.

Q2. Write the equation for Gibbs phase rule and define each of the terms.

Q3. What is a binary isomorphous alloy system?

Q4. What are the four Hume-Rothery rules for the solid solubility of one element in another?

Q5. Derive the lever rule for the amount in weight percent of each phase in two-phase regions of a binary phase diagram.Use a phase diagram in which two elements are completely soluble in each other.

Q6. Consider an alloy containing 70 wt % Ni and 30 wt % Cu (see Fig. 8.5).(a) At 1350°C make a phase analysis assuming equilibrium conditions. In the phase analysis include the following:

(i) What phases are present?(ii) What is the chemical composition of each phase?(iii) What amount of each phase is present?

(b) Make a similar phase analysis at 1500°C.(c) Sketch the microstructure of the alloy at each of these temperatures by using circular microscopic fields.

Q7. Describe how the liquidus and solidus of a binary isomorphous phase diagram can be determined experimentally.

Q8. Consider the binary eutectic copper-silver phase diagram in Fig. 8.32. Make phase analyses of an 88 wt % Ag–12 wt % Cu alloy at the temperatures (a) 1000°C, (b) 800°C, (c) 780°C +ΔT , and (d) 780°C -ΔT . In the phase analyses, include:(i) The phases present(ii) The chemical compositions of the phases(iii) The amounts of each phase(iv) Sketch the microstructure by using 2 cm diameter circular fields.

Q9. A Pb-Sn alloy (Fig. 8.13) contains 40 wt % β and 60 wt % α at 50°C. What is the average composition of Pb and Sn in this alloy?

Q10. An alloy of 30 wt % Pb and 70 wt % Sn is slowly cooled from 250°C to 27°C (see Fig. 8.13).(a) Is this alloy hypoeutectic or hypereutectic?(b) What is the composition of the first solid to form?(c) What are the amounts and compositions of each phase that is present at 183°C + ΔT ?(d) What is the amount and composition of each phase that is present at 183°C - ΔT ?(e) What are the amounts of each phase present at room temperature?

Q11. Consider an Fe–5.0 wt % Ni alloy (Fig. 8.18) that is slowly cooled from 1550 to 1450°C. What weight percent of the alloy solidifies by the peritectic reaction?

Q12. Determine the composition in weight percent of the alloy in the Fe–Ni system (Fig. 8.18) that will produce a structure of 40 wt % δ and 60 wt % γ , just below the peritectic temperature.

Q13. For an alloy of Cu–70 wt % Pb (Fig. 8.25), determine the amounts and compositions in weight percent of the phases present at (a) 955°C + ΔT , (b) 955°C - ΔT , and (c) 200°C.

Q14. Write equations for the following invariant reactions: eutectic, eutectoid, peritectic, and peritectoid. How many degrees of freedom exist at invariant reaction points in binary phase diagrams?

Q15. How are eutectic and eutectoid reactions similar? What is the significance of the -oid suffix?

Q16. Consider the aluminum-nickel (Al-Ni) phase diagram of Fig. 8.34. For this phase diagram:(a) Determine the coordinates of the composition and temperature of the invariant reactions.(b) Write the equations for the three-phase invariant reactions and name them.(c) Label the two-phase regions in the phase diagram.