2. Answer the following questions using the diagrams given for AISI 4340 steel (containing 0.4% C by weight). a) Which diagram shows ZSD and which diagram shows SSD? b) Name the phase regions in both diagrams. e) Define the critical cooling rate and using the SSD diagram, determine the critical cooling rate of this steel. d) For this steel, specify the temperature and minimum time to be applied to obtain 100% bainite as soon as possible. e) Can 100% bainite be formed by applying continuous cooling from austenite to this steel? ) Write down the phases that will occur if this steel is subjected to continuous cooling at average cooling rates of 0.01 ° C / s, 0.2 ° C / s and 10 ° C / s. g) This steel is rapidly cooled from 750 ° C to 650 ° C, kept at this temperature for 10 seconds, then cooled to 400 ° C rapidly and 10? What phases does it contain if cooled to temperature? h) Coarse pearlite, fine pearlite on the ZSD diagram of the steel; Show the upper bainite and lower bainite regions. Why are the transformation start and end curves in the form of "C" for diffusion-dependent phase transformations in ZSD diagrams? I) Why are martensite transformations shown between two straight lines in ZSD diagrams? 

800 800 700 700 600 500 g Sick C 400 300 200 100 Scaklk (C) 600 500 400 300 200 100 I 10 10 0 10 10 105 106 1 Zaman (s) 8.3C/s 10.006 10.02C's 10 10 102 103 104 Zaman (s) 105 106