for BCC n=2 & a=4R/sqrt3, for SC n=1 & a=2R
Question 1
Supercooling is the process of cooling a liquid above its freezing point.
FALSE!!! Supercooling a substance below its freezing point
FALSE!!!
Question 2
Alloying elements are added to improve ductility and to prevent hardness improvements.
TRUE!!! Alloying elements are added to metals primarily to modify their properties and enhance specific
characteristics.
Question 3
Sintering is carried out above the melting temperature so that a liquid phase is normally present.
FALSE!!! sintering is a process conducted below the melting point of a material to promote particle bonding and
densification, and the presence of a liquid phase is not a standard requirement for sintering.
Question 4
Binary phase diagrams cannot be used in predicting phase transformations and the resulting microstructures.
False, Binary phase diagrams are valuable tools in predicting phase transformations and the resulting microstructures
in materials science and metallurgy. A binary phase diagram illustrates the phases that are present at equilibrium for a
given combination of two components (usually elements or compounds) at a specific temperature and pressure.
Question 5
There is a strong correlation between the microstructure and mechanical properties of an alloy, which is also related to
the characteristics of its phase diagram.
TRUE!!! the microstructure of an alloy, which refers to the arrangement of phases and grain structures at the
microscopic level, plays a crucial role in determining the mechanical properties of the material. The phase diagram of
the alloy provides valuable insights into the relationships between composition, temperature, and the resulting
phases, which, in turn, influence the alloy's microstructure and mechanical behavior.
Question 6
When some a pure element is alloyed, the shape of the cooling curve changes.
True, when a pure element is alloyed with one or more other elements, the shape of the cooling curve can undergo
significant changes. The cooling curve represents the temperature changes of a material as it goes through the process
of solidification or cooling from a higher temperature to a lower one.
Question 7
Water quenching is used to minimize distortion and avoid fracture of the sample by forming martensite.
FALSE!!!
Water quenching is a rapid cooling process used in metallurgy to achieve specific material properties, particularly in
the context of heat treatment. The statement you've made is correct in the sense that water quenching is often
employed to minimize distortion and avoid fracture by promoting the formation of martensite, a specific crystalline
structure.
Question 8
There is a strong correlation between the microstructure and mechanical properties of an alloy, which is also related to
the characteristics in the phase diagram.
TRUE!!! the relationship between the phase diagram, microstructure, and mechanical properties is a fundamental
aspect of materials science and metallurgy. Engineers and metallurgists leverage this understanding to design and
tailor alloys for specific applications, ensuring that the final material meets desired performance criteria.
Question 9
Material’s properties are dependent of component’s shape and size.
FALSE!!!
Question 10
Hardness is a term used to describe the ability of an alloy to be hardened by the transformation from austenite to
martensite as a result of an appropriate heat treatment.
FALSE!!!
Question 11
PARALLEL!!!
Cite the relative orientation of the burgers vector and screw dislocation?
The Burgers vector (b) and the line direction of a screw dislocation are parallel to each other. In a screw dislocation, the
atoms are displaced along the dislocation line, and the Burgers vector represents the magnitude and direction of this
atomic displacement.
For a screw dislocation, the Burgers vector (b) is parallel to the dislocation line direction. Mathematically, this
relationship is expressed as:
b∥Dislocation Line
This is a characteristic feature of screw dislocations, which differ from edge dislocations where the Burgers vector is
perpendicular to the dislocation line. In the case of a screw dislocation, the atoms are displaced parallel to the
dislocation line as the dislocation moves through the crystal lattice. This results in a helical or spiral motion of the lattice
around the dislocation line.
Question 12
LIQUID AND 𝝐 !!! / (𝝐 + 𝑳)𝑷𝒉𝒂𝒔𝒆 !!!
Question 13
What concept would you use to calculate stress in a sample that is subjected to elastic deformation?
Hooke’s Law, Hooke's Law describes the linear relationship between stress (σ) and strain (ε) in the elastic deformation
region for many materials. 𝝈 = 𝑬𝝐
Question 14
What is hybrid composite?
A hybrid composite refers to a composite material that is composed of two or more different types of reinforcing
fibers or materials combined with a matrix. In composite materials, the goal is often to combine the desirable
properties of different components to create a material with improved overall performance. The term "hybrid"
indicates the mixing of diverse materials within the composite structure.
Question 15
A sample is subjected to a stress that is above its elastic limit, but before the yield strength; there, the sample?
Plastic Deformation, when a sample is subjected to stress that is above its elastic limit but below the yield strength, it
experiences plastic deformation. The elastic limit is the maximum stress a material can withstand without undergoing
permanent deformation. Beyond the elastic limit and up to the yield strength, the material undergoes plastic
deformation, which means that it will experience permanent, non-reversible changes in shape.
Question 16
A: Liquidus = between (𝜶 + 𝒍𝒊𝒒𝒖𝒊𝒅)
B: Solidus = between 𝜶 𝒂𝒏𝒅 (𝜶 + 𝒍𝒊𝒒𝒖𝒊𝒅)
C: Solvus = between 𝜶 𝒂𝒏𝒅 (𝜶 𝒂𝒏𝒅 𝜷)
D: Eutectic Line = line which connects intersection of solidus and solvus line on both side of binary eutectic phase
diagram
Question 17
Are FCC and BCC metals more ductile than HCP metals, if so why?
YES!!! More available slip syst… the differences in crystal structures and the availability of slip systems play a
significant role in determining the ductility of metals. FCC and BCC metals, with their more favorable crystal structures
for dislocation motion, tend to be more ductile than HCP metals.
Question 18
How do you identify the matrix in a composite?
Visual inspection, microscopy, chemical analysis, thermal analysis, density measurements, solubility tests, x-ray
diffraction, ultra-sonic testing
Question 19
From the following crystalline structure, indicate the densect(s) and give the approximate atomic packing factor?
Simple Cubic (SC): 0.52
Body-Centered Cubic (BCC): 0.68
Face-Centered Cubic (FCC): 0.74
Hexagonal Close-Packed (HCP): 0.74
Question 20
In pure aluminum, identify the atoms for self and substitutional diffusion respectively.
Question 21
What is the strain offset for the yield stress?
0.2%
Question 22
ACTIVATION ENERGY!!! Energy required for the formation of a vacancy.
Question 23
From the following ANSI steels, which one possesses the highest hardness after quenching?
4340 !!! then 1540…In the carbon/alloy grading system, the first digit represents the main alloying elements while the
second represents the top-grade elements that are added. The third and fourth digits together indicate the amount of
carbon in the alloy.
Question 24
What is a slip system?
The slip system consists of a slip plane and a slip direction, these orientations are dependent on interstitial atoms
Question 25
When two metals have similar atomic radii and crystal structures. Ag-Au!!!
Question 26
The concept known as “Endurance Limit” in high cycle fatigue is used to determine the approximate “safe” stress level
under dynamic loading. In order to determine the endurance, limit the sample is tested under high cycle fatigue must
resist at least:
10,000,000 or 106
Question 27
In a binary phase diagram that is at equilibrium, this information is always available: the phases that are present, the
compositions of these phases, its microstructure and the wt.% of the phases.
True
Question 28
Binary diagrams are plots that show the relationship between temperatures, pressure and composition. They cannot
provide information about melting, casting and crystallization phenomena of components.
FALSE!!! Binary phase diagrams do, in fact, provide valuable information about the melting, casting, and
crystallization phenomena of components in a material system. Binary phase diagrams depict the relationships
between temperature, pressure, and composition for two components (or elements) in a system.
Question 29
Binary phase diagrams represent the relationship between temperature, the compositions and quantities of phases at
equilibrium, which influence the microstructure of an alloy.
TRUE!!!
Question 30
What are the main strengthening mechanisms in metals?
a through d) !!!
Grain size
Cold working
Solid Solution
Precipitation strengthening
Question 31
Cite two quantum-mechanical concepts associated with the Bohr model of the atom
(1) that electrons are particles moving in discrete orbitals
(2) electron energy is quantized into shells.
Question 32
Number the following bonds from strongest (a) to the weakest (d)?
(a) Van der walls, secondary or hydrogen bond
(b) Metallic
(c) Covalent
(d) Ionic
Ionic, Covalent, Metallic, Vander walls
Question 33
What is the main purpose of the impact toughness, or Charpy test?
Measures the energy absorbed by a standard notched specimen while breaking under an impact load.
Question 34
What is the critical shear stress?
The minimum stress at which dislocations are activated!!!
Question 35
What the groups in the periodic table represent?
The number of electrons in the outer orbital
Question 36
What is a hybrid composite?
fiber-reinforced composite prepared by moulding two or more different kinds of fibers in a single matrix.
Question 37
Fick's 2nd law:
Whats the difference between 1st one?
1st law is in steady state
2nd law is with respect to time
Question 38
What is J in the following equation…
Diffusion Flux
Question 39
Limit where Hooke’s Law is valid?
ELASTIC LIMIT!!! / Proportionality Limit
Question 40
In this unit cell the top and bottom faces consist of six atoms that form regular hexagons and surround a single atom in
the center. Another plane that provides three additional atoms to the unit cell is situated between the top and bottom
planes
HCP
Question 41
What is the conventional sintering temperature? (Tm = melting point)
135°C-160°C or 60% and 80% of melting point of material
Question 42
The following equation is used to determine the theoretical density of crystalline materials?
Identify n and parameter to calculate Vc
n = # of atoms in unit cell
Vc = volume of cell
Question 43
What property should be improved to prevent fatigue failure?
Improve surface finish through polishing
Question 44
Substitutional diffusion requires the following defect to occur:
Dislocations
Question 45
From the following brackets, select the one used for atomic plane(s)
Plane = ( )
Direction = [ ]
Family { }
Question 46
____________ is the increase in the size of grains, it occurs by migration of grain boundaries in larger
grains towards smaller ones. Is also known as coarsening.
Grain Growth
Question 47
In terms of conductivity, the best material(s) should have:
FCC and Metallic bonding
Question 48
Define ac from the equation:
Critical crack length
Question 49
How many electrons are in the sub orbit f?
s-2
p-6
d-10
f-14
Question 50
What is Tm in the following equation?
Absolute melting temperature
Question 51
What is the other name for phase diagrams with complete solubility in solid and liquid?
Binary Isomorphous Systems
Question 52
Identify the stalking sequence of an FCC structure
SC - AAAAA
BCC - ABABABABAB
FCC - ABCABC
HCPC – ABABABAB
Question 53
What determines the properties in materials?
BOND!!! Atomic Structure and Inter-Atomic Bonding
Question 54
How many electrons are in the sub orbit p?
s-2
p-6
d-10
f-14
Question 55
A sample is subjected to a stress that is above its elastic limit, but before the Young Modulus; therefore, the sample?
DEFORMS PERMANENTRLY OR PLASTICALLY!!! Has plastically deformed.
Question 56
What does d define in the Bragg's law?
Lattice spacing
Question 57
What is the common effect of carburizing?
Increased hardness
Increased wear-resistance
Question 58
Are FCC and BCC metals being more ductile than HCP metals, why?
BECAUSE THEY HAVE MORE SLIP PLANES!!! FCC and BCC have a higher number of total slip systems.
Question 59
The critical resolve shear stress (tCRSS) is the stress identified as the minimum stress for?
Vacancy formation??? “Dislocation to form” is wrong!
Question 60
___________ is the driving force for sintering.
change in free energy from the decrease in surface area and lowering of the surface free energy by the replacement of
solid-vapor interfaces.
Question 61
Do all materials have the same slip system?
All metals do not have the same slip system. The reason for this is that for most metals, the slip system will consist of
the most densely packed crystallographic plane, and within that plane the most closely packed direction. This plane
and direction will vary from crystal structure to crystal structure.
Question 62
In quantum numbers, what does n means?
Question 63
From the following list, indicate the nature of each of the elements: inert gas, a halogen, an alkali metal, an alkaline earth
metal, or a transition metal.
a) 1s2 2s2 2p6 3s2 3p5
(b) 1s2 2s2 2p6 3s2 3p6 3d7 4s2
(c) 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6
(d) 1s2 2s2 2p6 3s2 3p6 4s1
(e) 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d5 5s2
(f) 1s2 2s2 2p6 3s2
a) Halogen
(b) Transition Metal
(c) Noble Gas
(d) Alkali Metals
(e) Transition Metal
(f) Alkaline Earth Metal
Question 64
Hardness is a term used to describe the ability of an alloy to be hardened by the transformation from austenite to
martensite as a result of an appropriate heat treatment.
FALSE!!! Hardenability is.
Question 65
What is the definition of the last two digits in the AISI steel designation (e.g. (10XX))?
the wt% carbon alloyed in
Question 66
Carburizing increases the ________ content in steel
Carbon
Question 67
In this point of a phase diagram a liquid phase transforms into two solid phases. The microstructure of the solid that
results from this transformation consists of alternating layers (sometimes called lamellae) of the phases that form
simultaneously during the transformation
Eutectic Point
Question 68
What the groups in the periodic table represent?
The number of electrons in the outer orbital
Question 69
How many atoms are in one g-mol of a pure element?
𝟔. 𝟎𝟐𝟐 𝒙 𝟏𝟎𝟐𝟑 𝒂𝒕𝒐𝒎𝒔
Question 70
Smaller grains always have better mechanical properties than larger grains.
NOT NECESSARILY!!! In most cases.
Question 71
Steady state diffusion is independent of what?
TIME!!!
Question 72
How many electrons are in the sub orbit s?
s-2
p-6
d-10
f-14
Question 73
Sintering atmosphere is not so important during the sintering process. Hence, only process time and temperature in the
furnace needs to be controlled for a successful sintering of parts.
True
Question 74
The Hume-Rothery rules are used to determine: ISOMORPHOUS SYSTEMS!!!
Question 75
What concept is used to determine the fraction of each phase?
LEVER RULE!!!
Question 76
____________Is the formation of a new set of strain-free and equiaxal grains equal dimensions in all directions that have
low dislocation and are characterized of the pre-cold-worked condition.
RECRYSTALLYZATION???
Question 77
What defines safety factor?
CONSECUENCES OF FAILURE, ACCURACY OF MEASUREMENT OF MECHANICAL FORCES, MATERIAL PROPERTIES AND
ECONOMICS. !!!