2002 Mid-term/ Dental Material/ Dental Alloy(I) 1. Grain size of a metal is not influenced by which of the following processing factor? A. cooling rate B. impurities C. heating rate D. shape of the casting mold 2. Which of the following elements is commonly used as a grain refiner for Au-Cu dental casting alloys? A. Ir B. Os C. Rh D. Ag 3. An alloy which is composed of two pure metal that are completely not miscible in the solid state. We call it a(an) A. solid solution B. eutectic alloy C. intermetallic compound D. peritectic alloy 4. Which of the following properties of a metal is not affected by the change of grain size of it? A. 0.2% yield strength B. tensile strength C. % elongation D. elastic modulus 5. Which of the following factors will determine whether or not and in what amount an ordered-solution lattice arrangement is going to form in a Au-Cu dental casting alloy? a. alloy composition b. heating rate c. cooling rate d. miscibility of alloying elements A. a, b, d B. b, c C. c, d D. a, c 6. Which of the following alloy has the best corrosion resistance than the others? A. Au-Cu B. Ag-Cu C. Pb-Sn D. Ag-Sn 7. The shape of grains in an orthodontic wire can be describe as A. polygonal B. fibrous C. circular D. amorphous 8. Which of the following properties will go up after solution-heat treatment of a Type III Au-Cu dental casting alloy? A. surface hardness B. 0.1% yield strength C. elastic modulus D. % elongation 9. Which of the following elements is not considered as a noble metal in dentistry? A. Ag B. Pd C. Ir D. Rh 10. Eutectic particle shows in the microstructure of a set dental amalgam might be which of the following ? A. Ag-Hg B. Sn-Hg C. Ag-Cu D. Ag-Sn Ans: CABDD ABDAC 第一题刘医师说casting mode的形状会影响冷却速度, 晶格形成状况也会受到 mold 形状的影响 so...C --

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