8. By atomic structure in metals, we refer to a) Geometric and dimensional defin

Question

8. By atomic structure in metals, we refer to a) Geometric and dimensional definitions of a metal component b) Packing of atoms in crystalline metal and packing defects c) Shape, size and size distribution of grains d) Size and distribution of second phase particles 9. Hardness in a quenched carbon steel is commonly adjusted by tempering a) At a temperature to achieve full austenite so as to gain high carbon solubility b) Above the eutectoid temperature so as to create equilibrium phases c) At different temperature in the region of 300-600°C below the eutectoid temperature d) At temperature close to the melting temperature 10. Why the Fe -C phase diagram cannot be used for prediction of phases in quenching process? a) Because phase diagrams are obtained in equilibrium conditions (i.e. slow cooling rate allow composition in phases to reach equilibrium) while quenching involves rapid cooling and is not an equilibrium process b) Because carbon can exist as solid solution, cementite or graphite C) Because Fe can also react with oxygern d) Because Fe can take different crystalline structure at different temperature 11. Full annealing of work hardened metal is often used to soften metal and restore ductility. At which of the followings stage most of the ductility is restored? a) Recovery stage b) Recrystallisation stage c) Grain growth stage d) None of the above 12. Based on the phase diagram in Fig. QA12, the nickel concentration in the liquid phase surrounding the solid particles at temperature c is a) 30 wt% b) 23 wt% c) 35 wt% d) 43 wt%

Explanation / Answer

8. Atomic structure of meyame is nothing but it's crystal structure. Atomic structure of metals tells about the packing of atoms and packing defects.

Hence option (b)

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