Dental Materials: Casting Alloys Study Guide for Engineers

The most important property for PFM alloy is

A) tensile strength

B) modulus of elasticity

C) density

D) yield strength

E) hardness

B) modulus of elasticity

For a proper alloy-porcelain compatibility, the metal alloy for PFM substructures should have

A) a slightly higher CTE than porcelain

B) a slightly lower CTE than porcelain

C) a CTE mis-match of 0.5x10^-6

D) the same CTE as porcelain

E) both A and C

E) both A and C

After firing and subsequent cooling, you want the porcelain to be bonded to the metal in a state of

A) harmony

B) tension

C) compression

D) matrimony

E) Illinois

C) compression

Interstitial solid solutions contain

A) solute atoms similar in size to solvent atoms

B) solute alloying elements at crystal lattice positions

C) solute atoms in spaces btw. solvent atoms

D) solute atoms in greater number than solvent atoms

C) solute atoms in spaces btw. solvent atoms

Copper alloying elements in gold alloys

A) increase strength

B) increase corrosion resistance

C) increase ductility

D) reduce hardness

A) increase strength

Rapid cooling/solidification of metals results in:

A) large grain, increased strength

B) large grain reduced strength

C) small grain, increased strength

D) small grain reduced strength

C) small grain, increased strength

True/False: Metals are the only materials with high thermal conductivity

True

Cold working metals

A) increase dislocation density resulting in material softening

B) increase dislocation density resulting in material hardening

C) decrease dislocation density resulting in material softening

D) decrease dislocation density resulting in material hardening

B) increase dislocation density resulting in material hardening

What are characteristics of metals?

luster, good conductors of heat + electricity, high density, high melting point, ductile, malleable

What is fabrication?

A) activities + processes that change the shape of metal by deforming it or removing metal

B) molten metal poured into mold or die

A) activities + processes that change the shape of metal by deforming it or removing metal

What is casting?

A) activities + processes that change the shape of metal by deforming it or removing metal

B) molten metal poured into mold or die

B) molten metal poured into mold or die

What are physical requirements for cast dental alloys?

- low MP (flow)

- moderately high density

- low coefficient of thermal expansion

What are chemical properties of dental alloys?

- chemical corrosion resistance

- electrochemical corrosion resistance

- solubility

What are mechanical properties of cast dental alloys?

- high E (stiffness)

- moderately high YS and H (resistance to plastic deformation)

- harden by heat treatment

What are biological properties of cast dental alloys?

- biocompatible (no toxic soluble phases)

- non-reactive in oral environment

True/False: softness and flexibility are disadvantages of gold

True

What are 3 ways to maximize close packing of similar size spheres?

body-centered cubic, face-centered cubic, hexagonal close packed

What is an alloy?

crystalline solid with metallic properties

Substitution solid solutions must have

A) solute atoms similar in size to solvent atoms

B) solute alloying elements at crystal lattice positions

C) solute atoms in spaces btw. solvent atoms

D) solute atoms in greater number than solvent atoms

A) solute atoms similar in size to solvent atoms

What are precious metals?

A) metals of high economic values

B) precious metal resistant to tarnish

C) alloys not containing precious metals to impart their corrosion resistance

A) metals of high economic values

What are examples of precious metals?

gold, iridium, osmium, palladium, platinum, rhodium, ruthenium, silver

What are noble metals?

A) metals of high economic values

B) precious metal resistant to tarnish

C) alloys not containing precious metals to impart their corrosion resistance

B) precious metals resistant to tarnish

True/False: silver is considered a noble metal

False

What are base-metal alloys?

A) metals of high economic values

B) precious metal resistant to tarnish

C) alloys not containing precious metals to impart their corrosion resistance

C) alloys not containing precious metals to impart their corrosion resistance

What are high noble metals?

A) contains at least 40% by weight gold / 60% by weight of noble metal elements

B) contains >/= 25% by weight noble metals

A) contains at least 40% by weight gold / 60% by weight of noble metal elements

What are noble metals?

A) contains at least 40% by weight gold / 60% by weight of noble metal elements

B) contains >/= 25% by weight noble metals

B) contains >/= 25% by weight noble metals

Type I and II gold alloys are

A) heat-hardenable

B) not heat-hardenable

B) not heat-hardenable

Type III and IV gold alloys are

A) heat-hardenable

B) not heat-hardenable

A) heat-hardenable

Low gold alloys are

A) alloys containing substantially less gold content

B) precious metal alloys not containing gold

A) alloys containing substantially less gold content

Gold-substitute alloys are

A) alloys containing substantially less gold content

B) precious metal alloys not containing gold

B) precious metal alloys not containing gold

What are requirement of PBM alloys?

alloy w/ high melting point, low thermal expansion, high strength

What is liquidus on a phase diagram?

A) temp btw. liquid and liquid solid mix

B) temp btw. liquid solid mix and all solid

A) temp btw. liquid and liquid solid mix

What is solidus on a phase diagram?

A) temp btw. liquid and liquid solid mix

B) temp btw. liquid solid mix and all solid

B) temp btw. liquid solid mix and all solid

Define a grain

single crystal in microstructure of a metal

Define a grain boundary

interface btw. adjacent grains in polycrystalline metal

Define a slip plane

alignment of internal planes between unit cells during crystallization

True/False: dislocations help prevent deformation in alloys

False

What is alloy strengthening/solid-solution strengthening?

A) adding another element to increase strength

B) interstitial clumps of atoms facilitate hardening

C) reducing grain size to prevent slip and dislocation

D) slowing rate of solidification by rapid cooling or quenching

E) seed molten metals with artificial nuclei

F) deformation at temperatures below melting point/plastic deformation

A) adding another element to increase strength

What is precipitate hardening?

A) adding another element to increase strength

B) interstitial clumps of atoms facilitate hardening

C) reducing grain size to prevent slip and dislocation

D) slowing rate of solidification by rapid cooling or quenching

E) seed molten metals with artificial nuclei

F) deformation at temperatures below melting point/plastic deformation

B) interstitial clumps of atoms facilitate hardening

What is grain size reduction hardening?

A) adding another element to increase strength

B) interstitial clumps of atoms facilitate hardening

C) reducing grain size to prevent slip and dislocation

D) slowing rate of solidification by rapid cooling or quenching

E) seed molten metals with artificial nuclei

F) deformation at temperatures below melting point/plastic deformation

C) reducing grain size to prevent slip and dislocation

What is metal solidification of hardening alloys?

A) adding another element to increase strength

B) interstitial clumps of atoms facilitate hardening

C) reducing grain size to prevent slip and dislocation

D) slowing rate of solidification by rapid cooling or quenching

E) seed molten metals with artificial nuclei

F) deformation at temperatures below melting point/plastic deformation

D) slowing rate of solidification by rapid cooling or quenching

What is heterogeneous nucleation?

A) adding another element to increase strength

B) interstitial clumps of atoms facilitate hardening

C) reducing grain size to prevent slip and dislocation

D) slowing rate of solidification by rapid cooling or quenching

E) seed molten metals with artificial nuclei

F) deformation at temperatures below melting point/plastic deformation

E) seed molten metals with artificial nuclei

What is cold working or strain hardening?

A) adding another element to increase strength

B) interstitial clumps of atoms facilitate hardening

C) reducing grain size to prevent slip and dislocation

D) slowing rate of solidification by rapid cooling or quenching

E) seed molten metals with artificial nuclei

F) deformation at temperatures below melting point/plastic deformation

F) deformation at temperatures below melting point/plastic deformation

True/False: a ordered state results in a hard state

True

True/False: slow cooling (bench top) results in large grain structure

True