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GRAND VALLEY STATE UNIVERSITY Course: EGR 250 — Materials Scienve School of Engineering & Engineering : Exam: _No. 2 Bachelor of Science in Engineering Date: Friday, November 11, 2022 Degree Program Time: 50 minutes General Instructions Circle or fill in the correct answer. Where required, you are expected to show clearly and completely how you arrived at your answers, and underline your final answers. Points will be lost if answers are cryplic, untidy, or badly arranged. Answer ALL of the Questions = 4 vV) Alle i Student Name 1. (4 points) What is the ratio between the shear stresses required for the (111)/[110] and (L10)/[111] slip systems in aluminum? Assume & in the Peierls-Nabarro stress equation is 2. The lattice parameter for aluminum is 0.404958 nm. a XK (a) Torpymi0) =1 3 Tarot ry Zena = 0.2863 as Toomty ©) Taryanio} = 2.259 Taroty Ty (dy) SP) = 0.4425 T 101TH) (e) None of the above wv (2 points) Which of the following point defects are found primarily in ionically bonded materials such as ceramics and are described as interstitial vacancy defects? (a) Vacancies VY Interstitial defects (c) Schottky defects depene ofthe defects None of the above 3 The density of a sample of beryllium with a close-packed hexagonal crystal structure is 1.844 Mg/m* and the lattice parameters are ao = 0.22858 nm and co = 0.35842 nm. Atomic mass of beryllium is 9.01 g/mol. (@ (3 points) Calculate the fraction of the lattice points that contain vacancies. (a) 8.50 x 10-4 % (b). 1.88 x 10-3 vacancies/m? “— 4.25 x 10-4 (d) 7.71 x 10°? 4 CE)8.50 x 10-4 vacancies/m* 12 x 10-4 g) None of the above aiope25-xams 11 
