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7.a) Describe the formation of pearlite, bainite, and martensite in the isothermal transformation. Mark each of it at the rig

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(A)Temp TE Eutectic temp 700 0 pearlite Gool 2 bainite 900 3 200 matensite lot 10 103 105 time

Pearlite is formed when the austenite is cooled slowly just below eutectice temprature. Line 1 and 2 shows the course pearlite and fine pearlite.

Bainite is formed when austenite is cooled very fast below the neck and then slowly cooled. Curve 3 shows the formation of bainite.

Martensite is formed when austenite is rapidly cooled to room temprature. Curve 4 shows the formation of martensite.

(B)

Course pearlite is prepared by cooling the austenite just below the eutectic temprature as shown in curve 1. Fine pearlite is prepared by cooling the austenite much below the eutectic temprature near about 540 degree celcius as shown in curve 2. Fine pearlite is harder than course beacause finer the pearlite it will have less tendency to slip which will lead to more sttong and hard.

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