mweeks_E54_W08_Discussion_07

mweeks_E54_W08_Discussion_07 - University of California,...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
ENGR54 – Principles of Materials Science and Engineering: Discussion 07 Principles of Materials Science and Engineering Discussion 07 Teaching Assistant: Matthew Weeks Chemical Engineering and Materials Science Henry Samueli School of Engineering University of California, Irvine [email protected] University of California, Irvine E54, Winter ‘08
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
ENGR54 – Principles of Materials Science and Engineering: Discussion 07 Isothermal Transformation Diagrams AKA Time-Temperature-Transformation (TTT) Diagrams What happens when we consider the kinetics of phase transformations? Time is an important factor.
Background image of page 2
ENGR54 – Principles of Materials Science and Engineering: Discussion 07 Transformations & Undercooling • Can make it occur at: ...727ºC (cool it slowly) ...below 727ºC (“undercool” it!) Eutectoid transf. (Fe-C System): γ α + Fe 3 C 0.76 wt% C 0.022 wt% C 6.7 wt% C Fe 3 C (cementite) 1600 1400 1200 1000 800 600 400 0 1 2 3 4 5 6 6.7 L γ (austenite) γ + L γ +Fe 3 C α +Fe 3 C L +Fe 3 C δ (Fe) C o , wt%C 1148°C T (°C) α ferrite 727°C Eutectoid: T Undercooling by T transf. < 727 ° C 0.76 0.022
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
ENGR54 – Principles of Materials Science and Engineering: Discussion 07 Isothermal Transformation Diagrams Fe-C system, C o = 0.76 wt% C Transformation at T = 675°C. 100 50 0 1 10 2 10 4 T = 675°C y , % transformed time (s) 400 500 600 700 1 10 10 2 10 3 10 4 10 5 0%pearlite 100% 50% Austenite (stable) Austenite (unstable) Pearlite T (°C) time (s) isothermal transformation at 675°C
Background image of page 4
ENGR54 – Principles of Materials Science and Engineering: Discussion 07 Eutectoid composition, C o = 0.76 wt% C Begin at T > 727°C Rapidly cool to 625°C and hold isothermally. Question 1: Effect of Cooling History On Microstructure α α α γ γ γ γ γ γ 400 500 600 700 0%pearlite 100% 50% Austenite (stable) T (727 ° C) Austenite (unstable) Pearlite T (°C) 1 10 10 2 10 3 10 4 10 5 time (s) γ γ γ a) b) c) d) What will the steel microstructure look like at the point indicated below?
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
ENGR54 – Principles of Materials Science and Engineering: Discussion 07 Eutectoid composition, C o = 0.76 wt% C Begin at T > 727°C Rapidly cool to 625°C and hold isothermally. Effect of Cooling History in Fe-C System 400 500 700 0%pearlite 100% 50% Austenite (stable) T (727 ° C) Austenite (unstable) Pearlite T (°C) 1 10 10 2 10 3 10 4 10 5 time (s) γ γ γ γ γ γ
Background image of page 6
ENGR54 – Principles of Materials Science and Engineering: Discussion 07 Transformations with Proeutectoid Materials Hyper eutectoid composition – proeutectoid cementite α C O = 1.13 wt% C T (727°C) T (°C) time (s) A A A + C P 1 10 10 2 10 3 10 4 500 700 900 600 800 A + P 3 1600 1400 1200 1000 800 600 400 0 1 2 3 4 5 6 6.7 L γ (austenite) γ + L γ +Fe 3 C α +Fe 3 C L +Fe 3 C δ (Fe) C o , wt%C T (°C) 727°C T 0.76 0.022 1.13
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
ENGR54 – Principles of Materials Science and Engineering: Discussion 07 Non-Equilibrium Transformation Products: Fe-C Bainite: -- α lathes (strips) with long rods of Fe 3 C --diffusion controlled.
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/14/2008 for the course E 54 taught by Professor Mumm during the Winter '08 term at UC Irvine.

Page1 / 41

mweeks_E54_W08_Discussion_07 - University of California,...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online