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MatSE 259 Exam 2 Review Session

MatSE 259 Exam 2 Review Session. Exam structure – same as Exam 1 Please write your student I.D. on the answer sheet Please mark your answers clearly Do not leave a question unanswered – there is no negative marking

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MatSE 259 Exam 2 Review Session

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  1. MatSE 259 Exam 2 Review Session Exam structure – same as Exam 1 Please write your student I.D. on the answer sheet Please mark your answers clearly Do not leave a question unanswered – there is no negative marking Hand in both question and answer sheets at the end of the exam – the questions will be posted on the website on Thursday after the last conflict exam

  2. Diffusion • Requirements: • Empty adjacent site • Sufficient energy • Types: • Interdiffusion or Impurity diffusion and Self diffusion • Vacancy diffusion and Interstitial diffusion • Steady-state diffusion: Fick’s first law

  3. Solid Solutions • A solid solution consists of at least two different atoms: solute and solvent. • The crystal structure of the solid solution is that of the solvent, and the solute atoms occupy either interstitial or substitutional positions. • Solubility limit depends upon: • Atomic Size • Crystal Structure • Electronegativity • Valences

  4. Fe-C (Fe-Fe3C) Phase Diagram • A phase diagram (equilibrium/constitutional diagram) shows the relationship between temperature and the composition and quantities of the phases of a system. • The (Fe-Fe3C) phase diagram tells you: • The phases present • The composition of the phases present • The fractions (mass or volume) of the phases present Eutectoid Reaction: • Hypo-eutectoid steels give pro-eutectoid a and pearlite • Hyper-eutectoid steels give pro-eutectoid CM and pearlite

  5. HYPOEUTECTOID HYPEREUTECTOID U V T V U Fe-C (Fe-Fe3C) Phase Diagram (contd.) Textbook Example 9.65

  6. Martensite (MAR) • Transforms from AUS on quenching or rapid cooling via a diffusionless shear process (CCP BCT) • Very hard and strong • Hardenability of a steel: ability to make MAR (depth of transformation to martensite) • Controlling the position of T-T-T plots: - Changing C content - Alloying - Increasing AUS grain size • MAR tempering produces tempered martensite; the mstructure of which consists of extremely small and uniformly dispersed cementite particles in a continuous ferrite matrix. Tempered Martensite is a lot tougher than MAR, depending on the tempering temperature.

  7. (c) (b) (a) T-T-T curves Textbook Example 10.15 Ms Mf

  8. (d) (c) (a) (b) T-T-T Curves Textbook Example 10.18

  9. Stainless Steels (Cr > 11% wt) • Based on the predominant mconstituent, S.S. are classified as: 1. Martensitic (heat treatable) Medium Cr, Low Ni, Medium-High C 2. Ferritic (not heat treatable) Medium Cr, Low Ni, Medium C a ferrite is the predominant phase 3. Austenitic (not heat treatable) High Cr, High Ni, Low C g phase extended to room temperature

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