21-Mat-A5 Phase Transformations and Thermal Treatment, December 2018: worked solutions

Paper format. National Exams, December 2018 — 12-Mtl-A5, Phase Transformations of Metals, Glasses and Ceramics. Three hours, closed book, approved Casio or Sharp calculator only. Eight questions of 20 marks each; the rubric states that five questions constitute a complete paper and only the first five appearing in the answer book are marked. All eight are answered here, because this set is a study resource rather than an exam script. Several sub-parts explicitly call for an essay-format answer, and the rubric rewards clarity and organisation, so those answers are written as structured prose with supporting sketches rather than as note form.

Note on the exam code

This December 2018 sitting's printed header reads 12-Mtl-A5, Phase Transformations of Metals, Glasses and Ceramics, covering the Fe-C phase diagram and microstructural design, precipitate solubility, precipitation hardening and spinodal decomposition, interfaces and precipitate-free zones, grain growth and Zener pinning, nucleation mechanisms, classical nucleation theory and constitutional supercooling, and glass and glass-ceramic processing.

Reference texts. The answers below are keyed to the works normally recommended for this syllabus code:

D. A. Porter, K. E. Easterling and M. Y. Sherif, Phase Transformations in Metals and Alloys, 3rd ed. — nucleation and growth theory (Ch. 4), precipitation hardening and spinodal decomposition (Ch. 5), solidification (Ch. 4), recrystallization and grain growth (Ch. 3).
W. D. Callister and D. G. Rethwisch, Materials Science and Engineering: An Introduction, 10th ed. — the Fe-Fe₃C phase diagram and microstructural development (Ch. 9–10), glasses and glass-ceramics (Ch. 12–13).
R. E. Reed-Hill and R. Abbaschian, Physical Metallurgy Principles, 4th ed. — binary phase diagrams and the lever rule, ordering and superlattices, nucleation kinetics.
F. C. Campbell (ed.), Phase Diagrams: Understanding the Basics, ASM International — precipitation sequences, coherent/semi-coherent/incoherent interfaces.
ASM Handbook, Vol. 4 (Heat Treating) and Vol. 9 (Metallography and Microstructures) — microconstituent identification and heat-treatment practice.
J. E. Shelby, Introduction to Glass Science and Technology, 2nd ed. — glass transition, glass-ceramic nucleation and crystallization schedules.

21-Mat-A5 Phase Transformations and Thermal Treatment: December 2018