MMET 206 Exam #1 Questions &
Answers
Name the 5 Material Properties that can be extracted from a Stress-Strain Diagram. Correct
Ans-Elastic Modulus
Yield Strength
Tensile Strength
Percent Elongation at Fracture
Toughness
What is the Unit Cell of Silicon? Correct Ans-Diamond FCC
How is a diamond's grade classified? Correct Ans-Classified by its shape (crystal planes)
Define an Allotropic Material Correct Ans-An element or material which exists in more than
one crystal structure
What fraction of elements in the Periodic Table are allotropic? How many allotropes does
Carbon have? Correct Ans-Over 1/4 of the elements in the periodic table are allotropic
Carbon has 8 allotropes
Give examples of chemical impurities Correct Ans-Factors that affect a diamond's color or
clarity, a steel's strength, etc.
,Describe chemical impurities Correct Ans-No material can be prepared without some degree
of chemical impurity
Impurities result in a solid solution (mixture), the mechanism for making metal alloys
Why are Crystal Defects not necessarily a bad thing? Correct Ans-Some crystal defects are
naturally occurring, and others are intentionally introduced to enhance material properties
Describe Substitutional solid solutions and name an example Correct Ans-The solute and
solvent atoms are roughly the same size
An example is NiCu Alloy
Describe Interstitial solid solutions and name an example Correct Ans-The solute atoms are
much smaller than the solvent atoms and squeeze in between them
An example is Steel Alloys
Vacancy and Interstitial Atom Defects occur in which types of materials? Correct Ans-Metals
and Elemental Materials
Imperfection Pair Defects occur in which types of materials? Correct Ans-Ionic Materials
(Ceramics)
Define Edge Dislocation Correct Ans-When a material is stressed above its yield strength,
dislocation motion occurs by sequential bonds breaking and forming
, What does a large number of dislocations in a material mean? Correct Ans-Dislocation
motion has taken place, and will result in plastic deformation
Define Screw Dislocation Correct Ans-Spiral stacking of crystal planes around the
dislocation line
Define Mixed Dislocation Correct Ans-Essentially a mixture of Edge and Screw Dislocations
Large scale of plastic deformation in cold rolling, forging, sheet metal forming, and stamping
etc. becomes possible because raw materials contain a huge number of dislocations
Define forging Correct Ans-A manufacturing process that artificially introduces many more
dislocations so they will interlock with each other
Name the three mechanisms that take place during the manufacturing process that prevent any
further dislocations from being easily done. Correct Ans-The exhaustion of existing
dislocations
The creation of many more dislocations
The entanglement (interlocking) of dislocations
Why are steels stronger than pure iron?
Why are ceramics the hardest materials? Correct Ans-These structures are harder for
dislocations to slide or move through
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