21-Mat-A5 Phase Transformations and Thermal Treatment, May 2013: worked solutions

Paper format. National Exams, May 2013 — 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. Several questions ask explicitly for essay-format answers, and the marking scheme rewards clarity and organisation, so the answers below are written as structured prose rather than as note form.

Note on the paper's subject

The printed exam header reads 10-Met-A5, Mechanical Behaviour and Fracture of Materials. The paper has no phase-transformation or heat-treatment question in the classical (TTT/CCT diagram, hardenability, tempering-curve) sense; the syllabus actually examined is deformation, strengthening, creep, fatigue, fracture, toughening, deformation processing and environmental degradation. 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 mechanisms (Ch. 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 and toughness, creep mechanisms and deformation-mechanism maps, case studies in toughening.
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 2013