a) A steel made up of 100% martensite is completely tempered to give an equilibrium composition consisting of 85 wt% ferrite and 15 wt% cementite. What was the carbon content of the austenite prior to quenching if this was a plain carbon steel?
b) Why do alloying additives like Ni, Cr, and Mo help form strong steels?
c) The transformation from austenite to pearlite+ferrite in a plain carbon steel follows Avrami kinetics. A linear relationship is found when ln(ln(1/(1-f)) is plotted on the y-axis and ln(t) is plotted on the x-axis. If the slope of this line is 0.675 and the y-intercept is 5.55, calculate the time in minutes is required for the reaction to reach 50% completion.