MSE 360 Phase Transformation and Diffusion Instructor Yuntian

MSE 360: Phase Transformation and Diffusion Instructor: Yuntian Zhu Office: 308 RBII Ph: 513 -0559 ytzhu@ncsu. edu Lecture 13 Department of Materials Science and Engineering 1 NC State University

Solidification in Action Department of Materials Science and Engineering 2 NC State University

Alloy Solidification T Equilibrium Solidification (Fig. 4. 20) T 1 T 2 T 3 XS XL TE XE X 0 Department of Materials Science and Engineering NC State University

Alloy Solidification No diffusion in Solid, Perfect Mixing in Liquid : Non-equilibrium level rule (Scheil Equation): XS = k. X 0(1 -fs)k-1 XL = X 0 f. Lk-1 Eutectic reaction always happen in Fig. 4. 21 Department of Materials Science and Engineering 4 NC State University

No Diffusion in Solid, Diffusional Mixing in Liquid D: Diffusivity, v = interface speed D/v = Characteristic width of concentration profile Fig. 4. 22, T T 1 T 2 T 3 XS XL TE XE X 0 Department of Materials Science and Engineering NC State University

Cellular and Dendritic Solidification Constitutional Supercooling: T Cell Structure: T 1 T 2 T 3 XS XL TE XE Dendritic structure: X 0 Condition for non-constitutional cooling: Department of Materials Science and Engineering NC State University

Eutectic Solidification λ > λ* Department of Materials Science and Engineering 7 NC State University

Off-Eutectic Solidification • Dendritic primary phase + eutectic structure (Fig. 4. 37) Department of Materials Science and Engineering 8 NC State University

Home Work • Reading assignment (to be quizzed at the next lecture): Ch. 4. 4 -4. 7 • HW: 4. 14, 4. 15, 4. 16, 4. 18, 4. 20. 4. 21 Department of Materials Science and Engineering 9 NC State University