Principles of Physical Metallurgy Prof. R. N. Ghosh ...文档.pdf

Principles of Physical Metallurgy Prof. R. N. Ghosh Department of Metallurgical and Materials Engineering Indian Institute of Technology, Kharagpur Lecture No. # 23 Iron – Carbon Phase Diagram (Refer Slide Time: 00:23) Good morning, last five classes we talked about process of solidification, and particularly with reference to I mean in general, I mean two hypothetical metals a and b, and how the solid, how the solidified form a metal. And how do you interpret it is structure, and what is the effect of composition on the structure, and we also talked about several invariant reactions. But all these were discussed in general using hypothetical cases. Today, we look at one specific phase diagram that is called iron carbon phase diagram, and we will see that with iron with carbon forms a compound called carbide, that is iron carbide which is known as cemented. And in fact, the first diagram that will talk about is actually iron, iron carbide phase diagram; and this forms the very basis of or describes the formation of the structure or one of the most commonly used material by human being, that is steel. And let us see that under this chapter that is iron carbon phase diagram. We will look at that allotropic transformation iron exists in several crystalline forms, and carbon can dissolve in this lattice of iron, and this solubility is a function of crystal structure and temperature. And we also will talk about a cementited phase which is iron carbide, it has a definite competition and because of the limited solubility of carbon in iron, and in the iron carbon phase diagram we do get several invariant reactions, we will look at th