MatSE 259 Exam 1 Review Session 1.Exam structure – 25 questions, 1 mark each 2.Do NOT forget to write your student I.D. on the answer sheet 3.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 Percent carbon (wt) x 100 Alloy content For example, 5060 has ???

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

Changing Mechanical Properties C content in steel Alloying elements Heat treatment - annealing, normalizing, tempering… Mechanical working - cold rolling, hot rolling, STRUCTURE changes

Differentiate between “phase” and “state”. Phase: A phase is a homogenous part of a system that has uniform physical and chemical characteristics. 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 T6 studied in class. For example, Al 2024-T4. Phase Diagrams

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

Impact Toughness 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 Mechanical properties (contd.)

Fracture Toughness testing Pre-cracked specimen Large K c  ductile fracture, small K c  brittle fracture Fractures Investigation of the fracture surface for the origin of crack: “Chevron’’ markings, striations, beachmarks Be able to recognize ductile fractures/ brittle fractures/ intergranular fractures/ transgranular fractures/ fatigue fractures…..

Most common crystal structures for metals are: -Cubic close-packed -Hexagonal close-packed Close-packed unit cells -A2 (“Body centered cubic”) close-packed; most densely packed Slip planes are the most densely packed planes in these structures. Crystal Structures

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

The ability of a metal to deform depends on the ability of the dislocation to move Restricting dislocation motion will strengthen the material. Methods: - solid solution hardening - grain size reduction - strain hardening (work hardening) - precipitation hardening (age hardening or aging) Dislocations (contd.)

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

Resolved Shear Stress  R =(F Cos )/(A Cos  )=  Cos  Cos The critical resolved shear stress is the least stress required to cause slip.

Temp Time Natural Aging T4

Properties Al 2024-O Tensile Strength179 MPa26000 psi Yield Strength75.8 MPa11000 psi Al 2024-T4 Tensile Strength469 MPa68000 psi Yield Strength 324 MPa47000 psi T4 (contd.)

Charpy/Izod Bar

Close-packed unit cells