Material Science Quizlet Exam 1

Metals

composed of one or more metallic elements and nonmetallic elements in very small amounts (<1%)

Metal Alloy

metallic substance composed of two or more metallic elements

Properties of Metals

Strong, ductile

High thermal & electrical conductivity

Opaque, reflective

Ceramics

compounds of metallic & non-metallic elements

Properties of Ceramics

Hard and strong but brittle

Non-conducting (electrical and thermal insulators)• Transparent, translucent, or opaque

Polymers

Organic compounds chemically based on C, H, and other nonmetallic elements

Composites

Combination of metal/polymer/ceramic to incorporate best characteristics of each component material

Interstitial vs Vacancy Mechanisms

Interstitial:

- in between atoms, to adjacent interstitial sites

-requires less energy

Vacancy:

- From one lattice site to an adjacent vacancy

- includes self and substitutional diffusion

-requires more energy

Burgers Vector-Dislocation Line Orientation: Edge

Perpendicular

Burgers Vector-Dislocation Line Orientation: Screw

Parallel

Burgers Vector-Dislocation Line Orientation: Mixed

neither parallel nor perpendicular

Hume-Rothery Rule for the Formation of Substitutional Solid Solution

Must have similar:

1) Atomic size

2) Crystal structure

3) Chemical Valance

4) Electronegativity

How are melting temperature and thermal expansion related?

Inversely!

Strong Bonds = High Melting Point, Low Thermal Expansion

Weak Bonds = Low Melting Point, High Thermal Expansion

Notation for Direction/Vectors

[ ]

Notation for Family of Direction/Vectors

< >

Notation for Planes

( )

Notation for Family of Planes

{ }

Atomic Packing Factor of HCP

0.74 (same as FCC)

Atomic Packing Factor of FCC

0.74 (same as HCP)

Atomic Packing Factor of BCC

0.68

Atomic Packing Factor of Simple Cubic

0.524

Allotropy

The possibility of the existence of two or more different crystal structures for a substance (generally an elemental solid).

The energy associated with 2-dimensional crystalline defects is generally in following sequence from the highest to lowest:

free surface (unfilled bonds = surface tension)

phase boundary (ex: solid-liquid)

high-angle grain boundary

low-angle grain boundary

coherent twin boundary

Which diffusion is faster, crystalline defects or lattice?

Diffusion through the crystalline defects such as surface/interface and grain boundaries is faster than diffusion through lattice.

Whose house?

Coogs House.