ENGR 220 Lecture 6 Chapter 3
All sections but 3.11
Quiz next week on chapter 2 and chapter 3 No equation provided
HW Week 3 4.1,4.5,4.6,4.26
Read Chapter 2 and 3 Read Chapter 4 for prep
I. 11.
Theoretical Density
Chapter 3:The Structure of Crystalline Solids
Theoretical Density,p Mass of Atoms in Unit Cell Density=p= Total Volume of Unit Cell
nA 0= VcNA
where
n=number of atoms/unit cell A=atomic weight Vc=Volume of unit cell=a3for cubic N=Avogadro's number =6.022x1023atoms/mol
Volume of Unit Cell A. Simple Cubic 0. B. FCC 1. a= 2Rv C. BCC III. Solidification A. Small Crystallite 1. Nuclei form 2. Own smaller formations B. Obstrute 1. Crystallites grow C. Grains
1. Individual crystalites have their own orientation D. Grain Boundaries 1. Metallic structures IV. Building Blocks A. Single Crystals 1. Properties a) Anisotropic 2. Some engineering applications require single crystals a) Diamond single crystals for abrasives b) Turbine Blades B. Polycrystals 1. Most engineering materials are polycrystals 2. Each grain is a single crystal 3. Randomly oriented grains towards the edges a) Isotropic /Equiaxed 4. Grains in weld zone are elongated a) Anisotropic C. Amorphous Metals 1. Glasses (Non Metals) a) Most common amorphous materials that one comes in contact with on a daily basis 2. Metals a) Although more challenging metals can be made amorphous b) No long range atomic order c) No grain boundaries 3. Rapid Solidification a) Produced via rapid solidification techniques in a short time 4. Properties a) Corrosion resistance D. Polymorphism and Allotropy 1. Distinct crystal structures 2. Titanium 3. Carbon 4. Iron V. Point Coordinates A.