MatSE 259 Exam 1 Review Session

MatSE 259 Exam 1 Review Session • Exam structure – 25 questions, 1 mark each • Do NOT forget to write your student I.D. on the answer sheet • Exams are sent to UTS for machine grading – please mark your answers clearly. No credit will be given if the machine cannot decipher your score

Steel designation • AISI-SAE numbering system for steels • XX XX Percent carbon (wt) x 100 Alloy content For example, 5060 has ???

Number Major alloy addition 1xxx - 2xxx Cu 3xxx Mn 4xxx Si 5xxx Mg 6xxx Mg & Si 7xxx Zn 8xxx other Aluminium alloy designation • Numbering system for Al alloys not the same as steels Numbering system also includes heat treatments – see website

Mechanical Properties Change due to; • C content in steel • Alloying elements • Heat treatment - annealing, normalizing, tempering… • Mechanical working - cold rolling, hot rolling, STRUCTURE changes

Phase Diagrams Differentiate between “phase” and “state” Phase diagram is a plot showing the relationship between temperature, composition and the quantities of phases in a system. On a phase diagram, you should be able to understand simple heat treatments, like the T4 studied in class. For example, Al 2024-T6.

Mechanical properties • Tensile testing • Elastic deformation – Plastic deformation – Yield • Hooke’s Law • Hardness testing • Penetration by indenter under load • Types – Rockwell, Brinell, Vickers, Knoop, Mohs • Hardness-strength conversion

Mechanical properties (contd.) • Impact Fracture testing • Charpy and Izod • Ductile-to-brittle transition • Creep testing • Primary, secondary, tertiary • Steady-state creep rate • Fatigue testing • S-N curves • Fatigue limit, fatigue strength, fatigue life • Investigation of the fracture surface for the origin of crack • “Chevron’’, striations, beachmarks

Dislocations • Dislocations move along slip planes – ductility • It is possible to plastically deform a material which contains dislocations

Crystal Structures • Most common crystal structures for metals are: • Cubic close-packed • Hexagonal close-packed • Body centered cubic • close-packed; most densely packed • Slip planes are the most densely packed planes in these structures.

Dislocations • The ability of a metal to deform depends on the ability of the dislocation to move • Restricting dislocation motion will strengthen the material; • - solid solution hardening • - grain size reduction • - strain hardening (work hardening) • - precipitation hardening (age hardening)

Dislocations Interactions • With each other • - annihilate • - entangle • - form generators • With grain boundaries • - disappear • - pile-ups

MatSE 259 Exam 1 Review Session