(0) (ii) Explain how an understanding of the creep failure mechanisms of high temperature nickel alloys has led to alloy and manufacturing developments which have resulted in an increase in the maximum operating temperature of a jet engine turbine blade. If we quench a plain carbon steel we can produce a very strong/hard and yet brittle material. Why does the quench lead to this change in properties, and what subsequent heat treatment would enable us to mostly retain the high strength whilst improving the ductility? Explain the effects of your proposed heat treatments in terms of the phase

Define quenching. (a) What effects does it have on the microstructure? (b) How does this affect dislocation movement? (c) Why/how does this affect the properties?

3-Miled steel can be converted into high carbon steel by which of the following heat treatment process: a- Normalizing b- Annealing c- Nitriding d- Case hardening 4-Which one of the following is the solid carburizing material: a-Charcoal b-NH4 c-NaOH d-CH4

3.The TTT diagram of a plain carbon steel is given in Fig. 1. Identify whether this steel is a hypoeutectoid, eutectoid or hypereutectoid steel. Explain why the transformation happens slowly at 850°C as well as at 300°C. Determine the microstructures expected in this type of steel after the following heat treatment processes. a) Austenize at 900°C, quench to 400°C and hold for 1000 s and quench to 25°C. b) Austenize at 900°C, quench to 25°C. c) Austenize at 900°C, quench to 675°C and hold for 1 s, quench to 400°C and hold for 900 s and slowly cool to 25°C. 900 Acm Cs 800 A1 FezC + Y 33 Fe3C + pearlite 45 700 Ps 600 ++ Fe3C + pearlite Y+ bainite Bs 500 46 Bainite 400 Yu Bf 300 57 Ms 200 60 Mf Y+ martensite 100 62 Martensite 102 65 103 104 105 106 0.1 1 10 Time (s) Fig. 1 Temperature (°C) Rockwell C hardness

Look up the standard aluminum alloy heat treatment temper designations. Use the designations to justify the yield strength behavior of the following aluminum alloys listed in Table 1.2: 2024-T3 vs. 2024-T6 and 7075-T6 vs. 7075-T73.

I. A full annealing is often utilized in low- and medium-carbon steels II. A ferritic transformation occurs when the quenching rate is rapid enough to prevent carbon diffusion III. Spheroidizing is the heat treatment method for these steels to develop a machinable and deformable structure Which statement(s) given above is/are correct?

Briefly explain the heat treatment steps of a tool steel by use of proper drawings and explainwhy multiple tempering is applied during heat treatment?

Austentitic stainless steel's are not hardenable by cold working however Austentic stainless steel's can be strengthened by heat treatment true or false?

(c) The steels with the following compositions are heat treated and the results of microstructures are indicated in Table 2(c). Table 2(c): Heat treated steels and the results of microstructures Steel A 0.35 wt% C Coarse Pearlite Steel B 0.25 wt% C Coarse Pearlite Steel C 0.35 wt% C Fine Pearlite Rank the above steels based on carbon content and microstructures from the highest to the lowest hardness with justification.

Refer to the Time Temperature Transformation (TTT) diagram given in Appendix A: (i) Determine the resulting microstructure for 0.8% carbon steel if the steel is rapidly cooled from the y region to 280°C within 5 seconds. (i) If the resulting microstructure in Question 6b (i) above is reheat to 300°C within 1 minute and hold for 1 hour at remain temperature, then and then rapidly quenched to room temperature, determine its final microstructure. (ii) If the resulting microstructure in Question 6b (i) above is reheat to 300°C within 1 minute and hold for 16 minutes at remain temperature, then and then rapidly quenched to room temperature, determine its final microstructure. (iv) Arrange the mircostructures 6 (b) (i,i and i) from the lowest to the highest hardnes value. (v) Sketch the thermal history from Question 6b (i) to (ii) on a TTT diagram.