True/False for Structures Final
For cubic crystals, as values of the Miller indices h,k, l decreases, the distance between adjacent and parallel planes decreases
FALSE
In a FCC structure, [100] is a close-packed direction
FALSE
In general, the physical properties of single-crystals and glasses are isotropic (i.e. do not depend on the direction of measurement)
FALSE
Point-defects are also created by the application of shear stress
FALSE
Since materials with no dislocations may be very strong but cannot be plastically deformed, therefore, dislocations weaken a material and makes the elastic deformation possible
FALSE
The concentration of dislocations in a solid follows the law of thermodynamics and is given, at equilibrium, by N_d=Nexp(-Q/kt)
FALSE
The equilibrium number of vacancies for a given quantity of material depends on temperature and decreases when temperature increases
FALSE
The fact that X-ray can ionize matter is used in the standard X-ray diffraction technique
FALSE
The grain size is often determined when the properties of a single crystalline material are under consideration, and the grain size has a significant impact of strength and response to further processing
FALSE
For a ductile material, all deformation up to the ultimate tensile stress is uniform throughout the sample. However at maximum stress, a small constriction (necking )begins to form
TRUE
In materials, dislocations are created by the application of shear stress
TRUE
Materials are not as strong as predicted by theory because flaws act as stress concentrators and lead to failure at stresses lower than theoretical values
TRUE
Materials with strong chemical bonds tend to have high melting points
TRUE
Plastic deformation in a metal is accomplished by means of point defects moving within preferred slip systems
TRUE
The bonds found in solid 'noble gases' (He, Ne, Ar, Kr, Xe, Rn) originate from the synchronization of electronic clouds, which induces weak, short-scale, attractive forces between induced electric dipoles
TRUE
The impurity defects in the solid solution are either substitutional or interstitial
TRUE
The solidification of a liquid alloy of eutectic composition yields a microstructure consisting of alternating layers of the two solid phases
TRUE
A brittle material can become ductile as temperature decreases
FALSE
As the dislocations density increases in a material, it becomes softer
FALSE
Ceramics are always ionic in nature
FALSE
The kinetics of a martensitic reaction is limited by the diffusion of species
FALSE
The yield strength is the maximum value of stress on an engineering stress-strain curve
FALSE
When repeated over and over, the stacking sequence ABABAB... yields a FCC structure
FALSE
A ductile failure has extensive plastic deformation in the vicinity of the advancing crack. Crack opening proceeds relatively slowly and any further extension requires increased levels of applied stress
TRUE
A system is at equilibrium when it is in its most stable state; that is when its phase characteristics do not change over time
TRUE
A young's modulus of a material is the slope of the stress-strain curve in the elastic deformation region, and is specific to each material
TRUE
Cold-working increases the yield strength and tensile strength and decreases the ductility of a material
TRUE
Cracks propagate if the stress at their tip exceeds a critical value. The largest and the most highly stressed crack will grow first
TRUE
Positions of the diffraction peaks (d_hkl) provide geometrical information of the crystal structure, and symmetry
TRUE
The addition of impurity atoms to a metal results in the formation of a solid solution
TRUE
The atomic linear density (LD) is defined as the number of atoms per unit length whose centers lie on the direction vector for a specific crystallographic direction
TRUE
The solubility of carbon in iron depends on temperature. This is why, upon cooling from a melt, steel will produce precipitates of carbon-rich phases
TRUE
There are no perfect crystals and many material properties are improved by the presence of imperfections
TRUE
Twinning occurs at low temperatures and high rates of shear loading (shock loading) conditions, where there are few present slip systems (restricting the possibility of slip)
TRUE
Unit Cell is the smallest repetitive volume which contains the complete lattice pattern of a crystal
TRUE
When temperature is sufficiently high compared to the melting point, atoms diffuse away from the initial position in a random-walk manner
TRUE
X-rays are ionizing radiations because their photon energy is larger than the binding energy of electrons in an atom
TRUE