Sample2 EXAM 2 Name Closed book, allowed a 5x7 card, calculator, and brain. Budget your time!

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1 MEEN Material Science Sample2 EXAM 2 Name Closed book, allowed a 5x7 card, calculator, and brain. Budget your time! Definitions: (10 terms, each definition is worth 1.5 points, 15 total) Match each term up with the best definition, note that some definitions may match more than one term, and there will be more definitions than terms. 1. Bainite 2. IT or TTT chart 3. Eutectic 4. Ductility 5. Cast iron 6. Carburizing 7. Recrystallization 8. Strain hardening 9. Fatigue Limit 10. Welding A. A measure of a material s ability to permanently deform without fracture. B. Increasing dislocation density to impede dislocation movement. C. Pounding on a metal until it breaks. D. Below this point one will get a layered micro-structure. E. Heating a material up until diffusion causes new grain growth F. A chart that was created through numerous nonequilibrium cooling tests, where crystal structure is determined. G. When increasing the number of cycles at a constant load does not tend to cause failure. H. A hard BCT material that resists indentation. I. A hardening method, based on movement of carbon through the steel. J. A high-temperature joining of two parts by melting them and adding filler material. K. A ferrous alloy with more than 2% carbon L. None of the above. Short Answers: (Choose the best answers, more than 1 may be correct, 4 points each, 28 total) 11. All of the following statements about fracture are correct, except (may be more than 1): a) Crack size does not affect fracture b) ductile fracture produces a cup and cone fracture c) in a brittle fracture there is measurable necking d) fatigue and corrosion can accelerate fracture 12. All of the following statements regarding metal fatigue are correct, except: a) Surface roughness decreases fatigue life. b) A cold-worked specimen will fail sooner. c) Carburizing treatment can improve fatigue life. d) A fatigue endurance limit is observed in pure aluminum. 13. All of the following statements about a eutectic alloy are correct except: a) The eutectic temperature is invariant. b) An alloy of eutectic composition solidifies over a range of temperatures. c) Two elements must be partially insoluble in the solid state to form a eutectic structure. d) Eutectic microstructure is easily detectible under a microscope. 14. All of the following statements about hardening are correct except: a) When a material changes from one crystal structure to another, it always is harder. b) Aging a PH metal will cause it to be more ductile. c) Bending a mild steel wire back and forth will cause it to cold work. d) A finer-grained polycrystalline metal will be harder than a coarse-grained one. 1

2 15. What properties do we get from a Jominy end-quench test? 16. Name 2 differences between steel and cast iron. 17. What is the difference between brass and bronze? Give an example where brass is used. (1) 1 point each, Circle True (T) or False (F). 18. T / F Titanium is considered the rich cousin to and is very similar to steel. 19. T / F Titanium is easier to machine and is lighter than aluminum. 20. T / F Powder metallurgy cannot be used if the metals do not form solid solutions. 21. T / F Casting cannot be used for intricate or large parts. 22. T / F Steel is the only magnetic material. 23. T / F Zinc is viscoelastic and always creeps under stress or strain. 24. T / F Magnesium is very heavy and will burn. 25. T / F Drawing is a fabrication method where a metal ingot is pulled through a die. 26. T / F Parts made by metal injection molding do not shrink after consolidation (sintering). 27. T / F A steel s ultimate strength is the same as its theoretical shear strength. 28. T / F The metal with the most close-packed slip systems will be the most ductile. 29. T / F Martensite has a hexagonal close-packed crystal structure. 30. (2.5) What is the best material for a reasonably-priced golf-club head. Briefly state why. 31. (2.5) 18. Why are the refractory metals so strong, stiff, and heavy? 2

3 32. (5) Given the phase diagram, calculate the approximate weight % of austenite and cementite in an steel with 1% carbon at 728 C. Show both calculations. 33. (5) Given the IT/TTT chart below, Draw your answer. A) Give a heat-treatment that will produce a steel bar that is 25% fine pearlite, 25% coarse bainite, and 50% martensite. B) If I want to take the above heat-treated steel, and transform it into 100% coarse pearlite, what should I do. Draw or write any conclusions below. 3

4 34. (10) In the table discuss 4 types of material failures. Briefly describe how to prevent each. Failure type Discussion & prevention 35. (15) You start work at a new company, ACME Ovens, and let your boss know that you understand metals and heat treatments. He comes to you the second day and says that they bought some new hinges that are needed to put a new oven together. The hinges are supposed to be a stronger stainless steel, while the old hinges tended to discolor after a month or two. However when the new hinges are used, they tend to crack easily when the oven doors are slammed shut. You can t get more of the old hinges for a month, and the new ovens need to be finished this week. What is the problem, and can you give him a solution using his own equipment? Discuss your solution and alternatives. 4

5 36. (5) General Questions, detach from test, all will get 5 points MEEN 3344 Spring 2004 Check the box that you most agree with. Strongly agree Agree Neutral Disagree Strongly agree The instructor treats all students the same. I understand the different types of failure and can recognize them. I understand the difference between crystalline and noncrystalline materials. I understand the basic heattreating process. This course will be useful as a practicing engineer. The computer projector is an effective tool in teaching this material. The student presentations are interesting and useful. I study harder so that I will not have to take the final. Ways to improve the course/ Comments 5