Question

5. What are the types of crystal defects? Give examples. (10 points) 6. Explain why the strength of a polycrystalline metal at room temperature decreases as its grain size increases. (10 points) 7. The ball of a ballpoint pen is 1 mm in diameter and has an ASTM grain size of 10. How many grains are there in the ball? (10 points) 8. Describe annealing and its effects. (10 points) 9. Which of the two tests, tension or compression, would require a machine with a higher loading capability, and why? (10 points) 10. Explain and differentiate ductile and brittle failure. (10 points) 11. Explain and differentiate fatigue and creep. (10 points)

Answer 1

Substitution impurity, distocations, Separations. 3 What the profound impact on ① Point defects the types of crystal defects I live examples Examples: Lattice Vacancies, self interstitial atoms, Crystal defects have a profound macroscopic properties of materials 6 Vacancy defects CO Interstitial defects (il Frenkel defects Schottky defects Edge Line defects ① Edge dislocation (1 Screw dislocation 1 Surface / Interface defects 6 Grain boundary defects () Twin boundary defects (li) Stucking faults ③ Volume defects 1 Dis persant defects (i) Precipitate defects Inclusion defects W Voids / Cracts de

® ③ Describe annealing and its effechi, During annealing process, the metal is heated a specific temperature where recrystallation occur. The metal is held at that temperature for a fixed period , then the cooling to room temperature. The cooling process must be done very slowly to produce a refined mierstructure thus maximising solthers. Generally annealing involve Effects of Annealing Cooling in an 0 Increase in ductility Decrease in hardness ② reduction of tensile strength ① reduction of metal's yield strength of Anmealing ☺ Fall annealing ① spheriodal annealing Process annea @ Diffusien annealing Types 3 Surtate sealing

differentiate ductile & brittle teilun Ductile fuilure; When a metu) (10) Explam and metul erolongates and then breakes it Brithe failure: when a metal u ductile facture. Ex: Mild steell breakes elongation is brittle failure, hi last arom without plastu deformation Ductile failure Brittle furlus 0 It involves large plastie 0 It is associated with deformation minimum o It u always preceeded to It does not involve by the localized deformation neekms. called "necking", o Ductile fracture normally a Brittle facture normally accurs through the grams follows the gram 6 It @ It occan suddenly tearing of the metal without any waming boundaries occus by slow

1) Explain the and different cate fatigue and creep ① Fatigue U. a term used to in for materials. When Fatigue a material is subjected to repeated stresses, it fuil at stress below the yeeld pont stresser. Such failure of a material is futique. The failure is caused by means of progressive crack formation which are usually fine and meroso pie sine. Usually considered m designing shatti, connecting rod, spongs et Creep: When a part u subjected to a constant stress at high temperature for a long period of time, it will undergo a slow and permanent deformation called creep, Property a considered m designma, Internal combustien eng mes, builen and turbines.