45 Final True/False
False
1040 plain carbon steel cannot be spheroidized.
False
According to the Hall-Petch equation, Ostwald ripening follows the empirical rule: dn d0 n Kt where n and K are material-dependent constants, t denotes time, d denotes average grain diameter at time t, and d0 denotes initial average grain diameter.
False
All metals (i.e., lead, tin) do strain harden when deformed at room temperature.
False
Aluminum alloys are the lowest-density metals used in aircraft construction.
False
Approximately 30% of the overall strength of fiberglass is contributed by the matrix.
False
At room temperature, the stress needed to cause significant creep will be lower for pure copper than for pure aluminum
False
BCC crystals do not contain dislocations.
False
Both the heat capacity and the specific heat capacity of amorphous polymers increase as the polymer is cooled through its glass transition.
True
Both the tensile strength and the yield strength of a metal can be increased by alloying.
False
Cathodic protection involves attaching a more cathodic material to a metal that you want to protect from corrosion.
True
Corrosion always involves the transfer of electrons.
False
Diffusion in crystalline solids can only occur if there are vacancies in the crystals.
False
Diffusion in crystalline solids can only occur if there are vacancies in the crystals.
False
Doubling t (using the same kind of steel) decreases the likelihood that the tank will undergo catastrophic failure at pressure P.
False
Doubling t (using the same kind of steel) does not affect the likelihood that the tank will undergo catastrophic failure at pressure P.
False
Fine-grained samples of y-iron contain fewer dislocations than coarse-grained samples of y-iron.
True
Given values of (i) the activation energy for self-diffusion in copper and (ii) the activation energy for vacancy migration in copper, we can calculate the activation energy for vacancy formation in copper.
False
Given values of the diffusion coefficient for carbon in iron at 850°C and 950°C, we can calculate the activation energy for the diffusion of carbon in iron.
False
If a material is undergoing secondary creep, then doubling the stress will double the strain rate
False
If material A has a higher stiffness than material B, material A must also have a higher proportional limit than material B.
False
If two different metals are in contact with each other while immersed in an aqueous environment, the metal with the smaller standard electrode potential will corrode.
False
If two pieces of clean, unpainted 1040 steel sheet are immersed near to each other (but not touching) in seawater, they will corrode at the same rate.
True
In any given intrinsic semiconductor, the mobility of holes in the conduction band is lower than the mobility of electrons in the conduction band.
True
In fiber reinforced composites, the dispersed phase will not have the same composition as the matrix phase.
False
In metals, dislocations provide easy pathways for conducting electrons.
True
Increasing crosslink density increases the Elastic Modulus.
False
Increasing the temperature of the tank's contents increases the likelihood that the tank will undergo catastrophic failure at pressure P.
False
Inorganic glasses are annealed by heating them to temperatures above the softening point.
False
Materials will not break if the applied stress is kept below the critical value predicted by the Griffith energy balance for crack propagation.
False
Metals are characterized by a high specific heat capacity, high thermal conductivity, and high electrical conductivity.
False
Metals are hardened by cold working because many of the dislocations have passed right through the grains and are no longer available to facilitate slip.
False
Metals subjected to a stress of 2E/1000 during a tensile test have not yet undergone any plastic deformation. (E = Young's modulus)
True
Necking occurs in metals that are subjected to a stress-strain test in which true stress is plotted against true strain.
False
Pearlite and bainite are examples of phases that can be formed by austenite if the cooling rate is controlled appropriately.
False
Plain carbon steels containing more than 0.76 wt% C do not contain ferrite.
True
Plastic deformation of a polycrystalline metal does not increase the density of the metal.
True
Replacing the steel tank with one made from an aluminum alloy increases the likelihood that the tank will undergo catastrophic failure at pressure P.
False
Sandwich panels are useful because of their high weight-to-stiffness ratio.
False
Self-interstitials do not form in pure metals.
False
Specific volume is the same as mass per unit volume.
False
The Burgers vector of a screw dislocation is normal to the dislocation line and parallel to the slip plane.
False
The Burgers vector of an edge dislocation is normal to the dislocation line and normal to the slip plane.
False
The addition of Ca to ZrO2 creates Shottky defects in the ZrO2.
False
The addition of Ge to Si produces an extrinsic semiconductor.
True
The addition of Mg to ZrO2 does not create Frenkel defects in the ZrO2.
True
The concept of a critical stress for crack propagation is applicable to both brittle and ductile materials.
False
The corrosion of a metal immersed in acid requires the presence of oxygen
False
The diffusion of oxygen atoms through a Ca-doped layer of ZrO2 is used to measure the concentration of oxygen dissolved in molten steel.
True
The formation of martensite does not depend on the concentration of vacancies.
False
The fracture toughness of a material is the energy required to break a unit volume of the material.
True
The hardenability of 1060 plain carbon steel does not depend on the hardness of the sample at room temperature prior to heat treatment.
False
The hardness exponent of some steels is equal to 0.15.
False
The hardness of precipitation-hardened alloys is maximized by ensuring that the precipitate particles are large.
False
The length of dislocation line per unit volume in a material equals the number of dislocations per unit area.
False
The melting temperature of semi-crystalline PP is not sensitive to tacticity.
True
The recrystallization temperature of brass is higher than the recrystallization temperature of copper.
False
The recrystallization temperature of bronze is lower than the recrystallization temperature of copper.
False
The stiffness of aligned discontinuous-fiber reinforced composites loaded along the fiber direction depends on the weight fraction of matrix in the composite.
False
The transformation of austenite to pearlite does not require diffusion.
False
Thermal conductivity depends on the ability of atoms to diffuse from warmer regions to cooler regions in a material.
False
Thermal shock resistance is promoted by a high thermal expansion coefficient and a high thermal conductivity.
False
To avoid breaking a material when it is being cold worked, it is necessary to perform the cold work in compression.
False
To avoid breaking a material when it is being cold worked, it is sufficient to perform the cold work in compression.
False
When a cold worked material is annealed, the microstructure at time t2 is coarser than the microstructure at time t1, if t2 > t1.
False
When a hole is created by thermal excitation of an electron across the band gap (1.1 eV) in silicon (atomic number 14), it has the same charge as a hole created by thermal excitation of an electron across the band gap (0.67 eV) in germanium (atomic number 32).
False
When a material is subjected to a cyclic stress, large cracks grow more slowly than small cracks.
False
When a metal exhibits a single, well defined freezing temperature, all the crystals formed on cooling will have the same composition.
False
When a microstructure consists of two solid phases formed by a binary alloy, the lever rule can be used to calculate the comp
False
When a reverse-bias potential is applied across a p-n junction in doped Si, the flow of charge carrier across the junction will be insignificantly small.
True
When a screw dislocation enables slip in a single crystal, the dislocation line remains in the slip plane.
True
When an overhead power line is fastened between utility poles and then subjected to a sharp frost, the conductor will experience increased mechanical tension.
False
When austenite containing 1.2 percent carbon by weight (and no significant amounts of any other alloying elements) is cooled slowly, hypereutectic Fe3C will form above 727°C.
False
When austenite containing 1.2 percent carbon by weight (and no significant amounts of any other alloying elements) is cooled slowly, hypereutectic Fe3C will form above 727°C.
False
When continuous-fiber reinforced composites are loaded longitudinally, the stress in the fibers equals the stress in the matrix.
False
When copper is stressed to just below its ultimate tensile strength, all the deformation is plastic.
True
When materials are subjected to a compressive stress, the Young's Modulus is always positive
False
When materials are subjected to a tensile strain, the lateral strain is always negative.
True
When materials are subjected to a tensile stress, the lateral strain is always negative.
False
When materials are subjected to a tensile stress, the lateral strain is always negative.
False
When metals are subjected to a tensile stress, the lateral strain is always positive.
False
When metals are subjected to a tensile stress, the strain is always proportional to the magnitude of the stress.
A
Which one of the following statements about metals is false? (a) High thermal expansion coefficients are associated with high melting temperatures. (b) High bond energies are associated with high melting temperatures. (c) High thermal expansion coefficients are associated with low stiffness. (d) Low bond energies are associated with high thermal expansion coefficients. (e) Low stiffness is associated with low melting temperatures.
False
Work hardening the steel decreases the likelihood that the tank will undergo catastrophic failure at pressure P.
