(a) Why is the Fe-Fe3C phase diagram a metastable phase diagram instead of a true equilibrium phase diagram? (1 points) (b) Define the following phases that exist in the Fe-Fe3C

phase diagram: (i) austenite, (ii) a ferrite, (iii)cementite, (iv) 8 ferrite. (2 points) (c) Write the reactions for the three invariant reactions that take place in the Fe-Fe3C phase diagram. (3points)