Week 2: Metals and Alloys

Question 1

an ___ is a mixture of metals

Answer 1

alloy

Question 2

___ are not so strong

____ are much more brittle

Answer 2

polymers, ceramics

Question 3

what is established by free electrons that are shared by all metallic ions in the structure?

Answer 3

bond

Question 4

what are the consequences of freedom of movement of e-?

Answer 4

high electric
heat conductivity
opacity

Question 5

metals are made of _____, which is opposite of amorphous/glassy material

Answer 5

crystals

Question 6

three common unit cells in dental metals

Answer 6

bcc-body centered cubic
fcc-face centered cubic
hcp-hexagonal close packed

Question 7

metals made of crystals have imperfections, such as…

Answer 7

point, line and plane defects

Question 8

alloying metals makes the resulting material ____ than pure metals

Answer 8

stronger

Question 9

why are alloyed metals stronger?

Answer 9

movement of dislocation is more difficult

Question 10

two types of solid solutions

Answer 10

substitutional, interstitial

Question 11

substitutional solid formed when two metals in alloy have the same ______

Answer 11

crystal lattice

Question 12

how many phases are present in solid solution alloys?

Answer 12

1 phase

Question 13

example of interstitial solid solution

Answer 13

stainless steel

Question 14

once the initial solid solution is formed, on further cooling the alloy under specific conditions, a precipitation of a 2nd phase occurs

Answer 14

partial solid insolubility

Question 15

what does the 2nd phase in partial solid insolubility do?

Answer 15

pins movement of dislocations

Question 16

compounds with well-defined composition/stoichiometry

Answer 16

intermetallic compounds

Question 17

two types of metal used in dentistry because of their highly corrosive resistant properties

Answer 17

• noble metals (alloys of Au, Pd)

- passivated alloys (Ti-alloys, stainless steel, Cr- alloy)

Question 18

examples of processing of metals

Answer 18

casting, machining, cold working, powder metallurgy

Question 19

metals only have ___ _____

Answer 19

metallic bonding

Question 20

consequences of metallic bonding

Answer 20

• high conductivity (thermal and electrical)
• opacity (e- absorb E.M. and photon energy)
• easily form alloys
• high plasticity

Question 21

a ____ ___ is one which shows ________ regular arrangement of atoms

Answer 21

crystalline material, long-range

Question 22

smallest repeating unit in a crystal

Answer 22

unit cell

Question 23

metals with bcc unit cells

Answer 23

Fe, Cr

Question 24

metals with fcc unit cells

Answer 24

Ag, Au, Cu

Question 25

metals with hcp/cph unit cells

Answer 25

Ti

Question 26

plane defects come from the discontinuity of _____ of the different crystals

Answer 26

boundaries