12. What material is considered the more expensive cousin to steel? Why?

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1 MEEN Material Science Spring 2003 EXAM 2 Name (1) Closed book, calculator, and brain. Budget your time! Definitions: (10 terms, each definition is worth 1.5 points, 15 total) Match each term up with it s definition, note that some definitions may match more than one term, and there will be more definitions than terms. 1. Martensite 2. IT or TTT chart 3. Eutectic 4. Ductility 5. Stainless steel 6. Carburizing 7. Recrystallization 8. Strain hardening 9. Fatigue Limit 10. Welding A. A hardening method, based on movement of carbon through the steel. B. A measure of a material s ability to permanently deform without fracture. C. When dislocation density impedes further dislocation movement. D. Pounding on a metal until it breaks. E. An alloy that doesn t follow the Hume- Rothery rules. F. An isotherm in the phase diagram G. A factor which relates how much a material will stretch to it s strength. H. A chart that was created through numerous non-equilibrium cooling tests, where crystal structure is determined. I. When increasing the number of cycles at a constant load does not tend to cause failure. J. A hard BCT material that resists indentation. K. A high-temperature joining of two parts by melting them or adding filler material. L. None of the above. Short Answers: (4 points each, 24 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. What material is considered the more expensive cousin to steel? Why? 13. 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. 1

2 14. What properties do we get from a Jominy end-quench test? 15. Name 2 differences between steel and cast iron. 16. What is the difference between brass and bronze? Give an example where brass is used. 17. (5) Given the phase diagram below, calculate the approximate weight % of austenite and cementite in an iron/steel with 2% carbon at 1000 C. Show both calculations. 2

3 18. (5) Given the IT/TTT chart below, Draw your answer. A) Give a heat-treatment that will produce a steel bar that is 50% fine pearlite, 25% fine bainite, and 25% 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. Remember that time can t be stopped. 3

4 Exam 2 Spring 2003 Name Open Book exam: (3 questions, 15 points each) You are allowed to use your book, a calculator, one 8½ x 11 sheet of paper, but no neighbor. Please be neat, and substantiate your answers as needed with references such as page or figure numbers. Use only material from chapters 7 through (15) Make a table and discuss the relative merits of welding, brazing and soldering. Discuss where each is useful, materials used, or used on, advantages and disadvantages. 4

5 2. (15) Suppose one had 3 specimens, one a cast iron of your choice, a beryllium/copper alloy, and a steel with a eutectoid composition (.76% carbon). You want each to have as high a tensile strength as possible, yet have reasonable ductility. a) What cast iron would you pick and why? b) What type of hardening or heat-treatment process would you use for each and why? c) What is a reasonable amount of ductility? (remember you have limited time, so concentrate on the main points first) 5

6 3. (15) You are to design a shear pin that will fail when a shear load of 300 lbs is applied to it. a) Pick a suitable material, and based on your calculations, give a diameter for the pin. b) Discuss why you picked that material. c) Are there any suitable alternatives? Discuss briefly. 6

7 4. (5) General Questions, detach from test, all will get 5 free points MEEN 3344 Spring 2003 Check the box that you most agree with. Strongly agree Agree Neutral Disagree Strongly agree The teacher treats all students the same. The instructor wants the students to learn the material The lectures are interesting and useful 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 studied harder so that I will not have to take the final. Comments 7