21-Mat-A5 Phase Transformations and Thermal Treatment, May 2014: worked solutions

Paper format. National Exams, May 2014 — 10-Met-A5, Mechanical Behaviour and Fracture of Materials. Three hours, closed book, any non-communicating calculator permitted. Eight questions of 20 marks each; the rubric states that five questions constitute a complete paper and that 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 questions ask explicitly for essay-format answers, and the marking scheme rewards clarity and organisation, so the discursive answers below are written as structured prose rather than as note form.

Note on the exam title

The printed exam header reads 10-Met-A5, Mechanical Behaviour and Fracture of Materials. The paper examines strengthening and deformation, creep and fatigue testing, fracture mechanics, toughening of engineering materials, deformation processing selection, and environmental degradation; it has no classical phase-transformation or heat-treatment (TTT/CCT diagram, hardenability, tempering-curve) questions. The answers below are written to the printed subject.

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

G. E. Dieter, Mechanical Metallurgy, 3rd ed. — strengthening and plastic instability (Ch. 3, 6), fracture (Ch. 7), fatigue (Ch. 12), creep and stress rupture (Ch. 13), forming processes (Ch. 15–19).
W. D. Callister and D. G. Rethwisch, Materials Science and Engineering: An Introduction, 10th ed. — strengthening (Ch. 7), failure: fracture, fatigue and creep (Ch. 8), composites (Ch. 16), corrosion and degradation (Ch. 17).
M. F. Ashby and D. R. H. Jones, Engineering Materials 1 & 2 — fast fracture, the transition flaw size, toughening mechanisms, and forming-process case studies.
ASM Handbook, Vol. 11 (Failure Analysis and Prevention), Vol. 14A (Metalworking: Bulk Forming) and Vol. 19 (Fatigue and Fracture) — process selection, fractography and environmental cracking.
Test standards cited where relevant: ASTM E8/E8M (tension), E139 (creep and stress rupture), E466 (constant-amplitude axial fatigue), E647 (fatigue crack growth rate), E399/E1820 (fracture toughness); NACE MR0175/ISO 15156 for sour service.

21-Mat-A5 Phase Transformations and Thermal Treatment: May 2014