4Metals&Alloys

Question 1

Rapid cooling forms more nuclei per unit volume and _______ the grain size.

Answer 1

decreases

Question 2

What type of grained alloys are desirable in dentistry?

Answer 2

Fine Grained Alloys!!

Question 3

What are the two properties that describe a metal’s ability of atomic centers to slide against each other into new positions within the same crystal lattice?

Answer 3

Ductility and Malleability

Question 4

What does the Finer Grain Size do to Yield Strength? Ductility? and the Ultimate Strength? What are the changes in these properties RELATED TO??

Answer 4

INCREASES Yield Strength….INCREASES ductility….Increases the Ultimate Strength…..THESE changes are RELATED to PLASTIC DEFORMATION and FRACTURE (think about the graph!)

Question 5

On the other hand, a material will fracture because a crack opens up on a grain boundary. This is more likely to occur in _____ _____ metals when the planes can not be slipped into the adjacent grains.

Answer 5

LARGE GRAIN

Question 6

What is the name for the mechanism of plastic deformation?

Answer 6

Dislocation Motion

Question 7

What is another name for COLD working a metal?

Answer 7

Wrought

Question 8

What is the term for causing plastic deformation by hammering, drawing, cold forging, cold rolling or bending that produces many dislocations that can not slip easily
through each other as the lattice becomes more distorted and grains are broken down and entangled in each other.

Answer 8

Cold Working/Wrought

Question 9

What is the area on a phase diagram underneath the liquid, but above the solid?

Answer 9

The Melting RANGE

Question 10

What is the result of cooling a soluble group of metals?

Answer 10

A solid solution

Question 11

What is the result of cooling a NON soluble group of metals?

Answer 11

A EUTECTIC solution

Question 12

What is the 3rd outcome of mixing metals if it is not solid or eutectic?

Answer 12

an intermetallic compound

Question 13

What was our example of 2 metals that are soluble and thus form a solid solution?

Answer 13

Au and Cu

Question 14

IN MIXING Cu and Au: At a certain % of Au they form an ______ ______ – Au and Cu occupy specific positions in the F-C cubic. _______ _______ impart higher hardness and strength to alloys.

Answer 14

Ordered Solution

Question 15

_______ _______ impart higher hardness and strength to alloys.

Answer 15

Ordered Solutions

Question 16

What happens when 2 metals are soluble as liquids, but NEARLY INSOLUBLE as solids?

Answer 16

A Eutectic Alloy!

Question 17

What about the phase diagram is very unique to a Eutectic Alloy?

Answer 17

It has a define MELTING POINT

Question 18

What is an everyday example of a eutectic alloy in dentistry?

Answer 18

AMALGAM!

Question 19

What is the ADA limit for amount of noble metals for an alloy to be considered a noble alloy? What would it be considered if it fell below that minimum?

Answer 19

25% or more of noble metals to be a noble alloy…Lower is considered a Base Metal

Question 20

ASIDE: what is a carat (k)?

Answer 20

1/24th of the whole (24k=pure gold)

Question 21

What does adding 10% Cu do to the tensile strength and the BHN of Au?

Answer 21

Adding 10% Cu TRIPLES both tensile strength and BHN!

Question 22

What does an ordered solution do for the Hardness, Elongation, and Yield strength of an alloy?

Answer 22

Ordered solution increases hardness, decreases elongation, and increases yield strength

Question 23

What are the two stipulations for High Noble metals?

Answer 23

Noble Metal of >60% and At least 40% Gold Content!!

Question 24

What is the requirement for Noble metal?

Answer 24

Noble metals >25% (NO gold stipulation)