The micrograph above shows a hypocutectoid steel that has been normalized. Norma

Question

The micrograph above shows a hypocutectoid steel that has been normalized. Normalization involves heating the steel until it is in a single phase state and letting it cool slowly. Estimate the % wt content of the eutectoid phase if the dark areas are the eutcctoid phase, and with reference to the phase diagram below, apply the lever rule to estimate the composition of the steel. Annotate the diagram below to show your working. From your answer to part c, what is the minimum temperature required for the normalization heat treatment? What do you predict the mechanical properties of the alloy shown in the micrograph will be like? Explain how the mechanical properties are related to the phase content and microstructure. What applications will it be useful for? If a thin specimen of the alloy is cooled very rapidly from the normalization temperature, sketch a diagram showing the microstructure that will result.

Explanation / Answer

% wt content =   (900/1200) * 100 %

                     =    75 %

=> minimum temperature required = 0.75 * 400 * 32/12

                                                        = 800 K

=> mechanical properties of alloy   =   hard, brittle and ductile

It is useful in making wires .

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