Question

From an iron-carbon phase diagram, plotted in terms of weight percent carbon:

A) What is the composition in weight percent of the iron-carbon alloy that has the lowest melting temperature? What is this melting temperature?

B) What is the composition in weight percent of the iron-carbon alloy that has the eutectoid composition? What is the eutectoid temperature?

C) What is the lowest temperature and weight percent carbon at which any iron-carbon alloy shows any amount of delta phase?

D) A particular iron-carbon alloy shows a final microstructure after slow cooling that consists of 80% proeutectoid ferrite and 20% pearlist. What is the carbon composition of this alloy, in weight percent?

E) At what temperature would the alloy from part d become all single-phase austentite on heating?

F) At what temperature would the alloy from part d become all liquid on heating?

Answer 1

Part A : the lowest melting temperature is where there is a Maximum solubility possible is 723^oc and its corresponding carbon % is 0.025% .at which austenite transformed to pearlite.

part B: Eutectoid composition is 0.8%carbon is where two phase mixture of ferrite and cementite at 723^oc

part c: lowest temperature that alloy shows delta phase is 1400^oc and 0.008% carbon. In range of 1400 to 1600 ^oc we can see delta phase and carbon range is 0.008 %to 0.10%

part D: 80%proeutectoid ferrite and 20%pearlite occurs at 0.166%carbon which occurs by using

(80/100)=([0.8-x]/[0.8-0.008]) which gives x=0.1664=carbon percent

part E: at 723^oc it becomes single phase austenite

Part F: at 1537^oc it become all liquid