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materials science engineering

Questions and Answers of Materials Science Engineering

Steady-state creep rate data are given below for nickel at 1000(C (1273 K): If it is known that the activation energy for creep is 272,000 J/mol, compute the steady-state creep rate at a temperature
Steady-state creep data taken for a stainless steel at a stress level of 70MPa (10,000psi) are given If it is known that the value of the stress exponent n for this alloy is 7.0, compute the
Cite three metallurgical/processing techniques that are employed to enhance the creep resistance of metal alloys.
An S-590 alloy component (Figure) must have a creep rupture lifetime of at least 100 days at 500(C (773 K). Compute the maximum allowable stress level.
Consider an S-590 alloy component (Figure) that is subjected to a stress of 200MPa (29,000psi). At what temperature will the rupture lifetime be 500h?
For an 18-8 Mo stainless steel (Figure), predict the time to rupture for a component that is subjected to a stress of 80MPa (11,600psi) at 700?C (973 K).
Consider an 18-8 Mo stainless steel component (Figure) that is exposed to a temperature of 500(C (773 K). What is the maximum allowable stress level for a rupture lifetime of 5 years? 20 years?
Consider the sugar?water phase diagram of Figure. (a)?How much sugar will dissolve in 1500 g water at 90?C (194?F)? (b) If the saturated liquid solution in part (a) is cooled to 20?C (68?F), some of
At 500°C (930°F), what is the maximum solubility(a) Of Cu in Ag?(b) Of Ag in Cu?
Cite three variables that determine the microstructure of an alloy.
Consider a specimen of ice that is at 210(C and 1 atm pressure. Using Figure, the pressure???temperature phase diagram for H2O, determine the pressure to which the specimen must be raised or lowered
At a pressure of 0.01 atm, determine(a) The melting temperature for ice, and(b) The boiling temperature for water.
Given here are the solidus and liquidus temperatures for the germanium-silicon system. Construct the phase diagram for this system and label eachregion.
Cite the phases that are present and the phase compositions for the following alloys:(a) 90 wt% Zn-10 wt% Cu at 400(C (750(F)(b) 75 wt% Sn-25 wt% Pb at 175(C (345(F)(c) 55 wt% Ag-45 wt% Cu at 900(C
Is it possible to have a copper–nickel alloy that, at equilibrium, consists of a liquid phase of composition 20 wt% Ni–80 wt% Cu and also an a phase of composition 37 wt% Ni–63 wt% Cu? If so,
Is it possible to have a copper-zinc alloy that, at equilibrium, consists of an e phase of composition 80 wt% Zn-20 wt% Cu, and also a liquid phase of composition 95 wt% Zn-5 wt% Cu? If so, what will
A copper-nickel alloy of composition 70 wt% Ni-30 wt% Cu is slowly heated from a temperature of 1300(C (2370(F).(a) At what temperature does the first liquid phase form?(b) What is the composition of
A 50 wt% Pb-50 wt% Mg alloy is slowly cooled from 700(C (1290(F) to 400(C (750(F).(a) At what temperature does the first solid phase form?(b) What is the composition of this solid phase?(c) At what
For an alloy of composition 74 wt% Zn-26 wt% Cu, cite the phases present and their compositions at the following temperatures: 850(C, 750(C, 680(C, 600(C, and 500(C.
Determine the relative amounts (in terms of mass fractions) of the phases for the alloys and temperatures given in Problem 9.8.(a) 90 wt% Zn-10 wt% Cu at 400(C (750(F)(b) 75 wt% Sn-25 wt% Pb at 175(C
A 1.5-kg specimen of a 90 wt% Pb???10 wt% Sn alloy is heated to 250oC (480oF); at this temperature it is entirely an a-phase solid solution (Figure). The alloy is to be melted to the extent that 50%
A magnesium-lead alloy of mass 5.5 kg consists of a solid α phase that has a composition that is just slightly below the solubility limit at 200oC (390oF).(a) What mass of lead is in the alloy?(b)
A 90 wt% Ag-10 wt% Cu alloy is heated to a temperature within the b + liquid phase region. If the composition of the liquid phase is 85 wt% Ag, determine:(a) The temperature of the alloy(b) The
A 30 wt% Sn-70 wt% Pb alloy is heated to a temperature within the a + liquid phase region. If the mass fraction of each phase is 0.5, estimate:(a) The temperature of the alloy(b) The compositions of
For alloys of two hypothetical metals A and B, there exist an ?, A-rich phase and a ?, B-rich phase. From the mass fractions of both phases for two different alloys provided in the table below,
A hypothetical A–B alloy of composition 55 wt% B–45 wt% A at some temperature is found to consist of mass fractions of 0.5 for both α and β phases. If the composition of the β phase is 90 wt%
Is it possible to have a copper-silver alloy of composition 50 wt% Ag-50 wt% Cu, which, at equilibrium, consists of α and β phases having mass fractions W = 0.60 and W β = 0.40? If so, what will
For 11.20 kg of a magnesium-lead alloy of composition 30 wt% Pb-70 wt% Mg, is it possible, at equilibrium, to have α and Mg2Pb phases having respective masses of 7.39 kg and 3.81 kg? If so, what
Derive Equations 9.6a and 9.7a, which may be used to convert mass fraction to volume fraction, and viceversa.
Determine the relative amounts (in terms of volume fractions) of the phases for the alloys and temperatures given in Problem 9.8a, b, and c. Below are given the approximate densities of the various
(a) Briefly describe the phenomenon of coring and why it occurs.(b) Cite one undesirable consequence of coring.
It is desirable to produce a copper-nickel alloy that has a minimum noncold-worked tensile strength of 350MPa (50,750psi) and a ductility of at least 48%EL. Is such an alloy possible? If so, what
A 45 wt% Pb–55 wt% Mg alloy is rapidly quenched to room temperature from an elevated temperature in such a way that the high-temperature microstructure is preserved. This microstructure is found to
Briefly explain why, upon solidification, an alloy of eutectic composition forms a microstructure consisting of alternating layers of the two solid phases.
What is the difference between a phase and a microconstituent?
Is it possible to have a copper-silver alloy in which the mass fractions of primary β and total β are 0.68 and 0.925, respectively, at 775oC (1425oF)? Why or why not?
For 6.70 kg of a magnesium-lead alloy, is it possible to have the masses of primary α and total α of 4.23 kg and 6.00 kg, respectively, at 460oC (860oF)? Why or why not?
For a copper-silver alloy of composition 25 wt% Ag-75 wt% Cu and at 775oC (1425oF) do the following:(a) Determine the mass fractions of α and β phases.(b) Determine the mass fractions of primary α
The microstructure of a lead-tin alloy at 180oC (355oF) consists of primary β and eutectic structures. If the mass fractions of these two micro constituents are 0.57 and 0.43, respectively,
Consider the hypothetical eutectic phase diagram for metals A and B, which is similar to that for the lead-tin system, Figure. Assume that (1) ? and ? phases exist at the A and B extremities of the
For an 85 wt% Pb-15 wt% Mg alloy, make schematic sketches of the microstructure that would be observed for conditions of very slow cooling at the following temperatures: 600°C (1110°F), 500°C
For a 68 wt% Zn-32 wt% Cu alloy, make schematic sketches of the microstructure that would be observed for conditions of very slow cooling at the following temperatures: 1000°C (1830°F), 760°C
For a 30 wt% Zn-70 wt% Cu alloy, make schematic sketches of the microstructure that would be observed for conditions of very slow cooling at the following temperatures: 1100°C (2010°F), 950°C
On the basis of the photomicrograph (i.e., the relative amounts of the microconstituents) for the lead?tin alloy shown in Figure and the Pb?Sn phase diagram (Figure), estimate the composition of the
The room-temperature tensile strengths of pure lead and pure tin are 16.8MPa and 14.5MPa, respectively.(a) Make a schematic graph of the room-temperature tensile strength versus composition for all
Two intermetallic compounds, AB and AB2, exist for elements A and B. If the compositions for AB and AB2 are 34.3 wt% A–65.7 wt% B and 20.7 wt% A–79.3 wt% B, respectively, and element A is
What is the principal difference between congruent and incongruent phase transformations?
Figure is the aluminum-neodymium phase diagram, for which only single-phase regions are labeled. Specify temperature-composition points at which all eutectics, eutectoids, peritectics, and congruent
Figure is a portion of the titanium-copper phase diagram for which only single-phase regions are labeled. Specify all temperature-composition points at which eutectics, eutectoids, peritectics, and
Construct the hypothetical phase diagram for metals A and B between temperatures of 600°C and 1000°C given the following information:● The melting
In Figure is shown the pressure?temperature phase diagram for H2O. Apply the Gibbs phase rule at points A, B, and C; that is, specify the number of degrees of freedom at each of the points?that is,
Compute the mass fractions of α ferrite and cementite in pearlite.
(a) What is the distinction between hypoeutectoid and hypereutectoid steels?(b) In a hypoeutectoid steel, both eutectoid and proeutectoid ferrite exist. Explain the difference between them. What
What is the carbon concentration of an iron–carbon alloy for which the fraction of total ferrite is 0.94?
What is the proeutectoid phase for an iron–carbon alloy in which the mass fractions of total ferrite and total cementite are 0.92 and 0.08, respectively? Why?
Consider 1.0 kg of austenite containing 1.15 wt% C, cooled to below 727(C (1341(F).(a) What is the proeutectoid phase?(b) How many kilograms each of total ferrite and cementite form?(c) How many
Consider 2.5 kg of austenite containing 0.65 wt% C, cooled to below 727(C (1341°F).(a) What is the proeutectoid phase?(b) How many kilograms each of total ferrite and cementite form?(c) How many
Compute the mass fractions of proeutectoid ferrite and pearlite that form in an iron–carbon alloy containing 0.25 wt% C.
The microstructure of an iron–carbon alloy consists of proeutectoid ferrite and pearlite; the mass fractions of these two microconstituents are 0.286 and 0.714, respectively. Determine the
The mass fractions of total ferrite and total cementite in an iron-carbon alloy are 0.88 and 0.12, respectively. Is this a hypoeutectoid or hypereutectoid alloy? Why?
The microstructure of an iron-carbon alloy consists of proeutectoid ferrite and pearlite; the mass fractions of these microconstituents are 0.20 and 0.80, respectively. Determine the concentration of
Consider 2.0 kg of a 99.6 wt% Fe–0.4 wt% C alloy that is cooled to a temperature just below the eutectoid.(a) How many kilograms of proeutectoid ferrite form?(b) How many kilograms of eutectoid
Compute the maximum mass fraction of proeutectoid cementite possible for a hypereutectoid iron–carbon alloy.
Is it possible to have an iron-carbon alloy for which the mass fractions of total ferrite and proeutectoid cementite are 0.846 and 0.049, respectively? Why or why not?
Is it possible to have an iron-carbon alloy for which the mass fractions of total cementite and pearlite are 0.039 and 0.417, respectively? Why or why not?
Compute the mass fraction of eutectoid ferrite in an iron-carbon alloy that contains 0.43 wt% C.
The mass fraction of eutectoid cementite in an iron-carbon alloy is 0.104. On the basis of this information, is it possible to determine the composition of the alloy? If so, what is its composition?
The mass fraction of eutectoid ferrite in an iron-carbon alloy is 0.82. On the basis of this information, is it possible to determine the composition of the alloy? If so, what is its composition? If
For an iron-carbon alloy of composition 5 wt% C-95 wt% Fe, make schematic sketches of the microstructure that would be observed for conditions of very slow cooling at the following temperatures:
Often, the properties of multiphase alloys may be approximated by the relationship where E represents a specific property (modulus of elasticity, hardness, etc.), and V is the volume fraction. The
A steel alloy contains 97.5 wt% Fe, 2.0 wt% Mo, and 0.5 wt% C.(a) What is the eutectoid temperature of this alloy?(b) What is the eutectoid composition?(c) What is the proeutectoid phase?Assume that
A steel alloy is known to contain 93.8 wt% Fe, 6.0 wt% Ni, and 0.2 wt% C.(a) What is the approximate eutectoid temperature of this alloy?(b) What is the proeutectoid phase when this alloy is cooled
Name the two stages involved in the formation of particles of a new phase. Briefly describe each.
(a) Rewrite the expression for the total free energy change for nucleation (Equation 10.1) for the case of a cubic nucleus of edge length a (instead of a sphere of radius r). Now differentiate this
If copper (which has a melting point of 1085°C) homogeneously nucleates at 849°C, calculate the critical radius given values of –1.77 × 109 J/m3 and 0.200 J/m2, respectively, for the latent heat
(a) For the solidification of iron, calculate the critical radius r* and the activation free energy ?G* if nucleation is homogeneous. Values for the latent heat of fusion and surface free energy are
(a) Assume for the solidification of iron (Problem 10.4) that nucleation is homogeneous, and the number of stable nuclei is 106 nuclei per cubic meter. Calculate the critical radius and the number of
For some transformation having kinetics that obey the Avrami equation (Equation 10.17), the parameter n is known to have a value of 1.7. If, after 100 s, the reaction is 50% complete, how long (total
Compute the rate of some reaction that obeys Avrami kinetics, assuming that the constants n and k have values of 3.0 and 7 ( 10-3, respectively, for time expressed in seconds.
It is known that the kinetics of recrystallization for some alloy obey the Avrami equation and that the value of n in the exponential is 2.5. If, at some temperature, the fraction recrystallized is
The kinetics of the austenite-to-pearlite transformation obey the Avrami relationship. Using the fraction transformed?time data given here, determine the total time required for 95% of the austenite
The fraction recrystallized?time data for the recrystallization at 600?C of a previously deformed steel are tabulated here. Assuming that the kinetics of this process obey the Avrami relationship,
(a) From the curves shown in Figure and using Equation 10.18, determine the rate of recrystallization for pure copper at the several temperatures. (b) Make a plot of ln(rate) versus the reciprocal of
Determine values for the constants n and k (Equation 10.17) for the recrystallization of copper (Figure 10.11) at 102?C.
In terms of heat treatment and the development of microstructure, what are two major limitations of the iron–iron carbide phase diagram?
(a) Briefly describe the phenomena of superheating and supercooling.(b) Why do these phenomena occur?
Suppose that a steel of eutectoid composition is cooled to 550°C (1020°F) from 760°C (1400°F) in less than 0.5 s and held at this temperature.(a) How long will it take for the
Briefly cite the differences between pearlite, bainite, and spheroidite relative to microstructure and mechanical properties.
Using the isothermal transformation diagram for an iron?carbon alloy of eutectoid composition (Figure), specify the nature of the final microstructure (in terms of micro constituents present and
Make a copy of the isothermal transformation diagram for an iron???carbon alloy of eutectoid composition (Figure) and then sketch and label time???temperature paths on this diagram to produce the
Using the isothermal transformation diagram for a 0.45 wt% C steel alloy (Figure), determine the final microstructure (in terms of just the microconstituents present) of a small specimen that has
For parts (a), (c), (d), (f), and (h) of Problem 10.20, determine the approximate percentages of the microconstituents that form.(a) Rapidly cool to 250(C (480(F), hold for 103 s, then quench to room
Make a copy of the isothermal transformation diagram for a 0.45 wt% C iron-carbon alloy (Figure), and then sketch and label on this diagram the time-temperature paths to produce the following
Name the microstructural products of eutectoid iron–carbon alloy (0.76 wt% C) specimens that are first completely transformed to austenite, then cooled to room temperature at the following
Figure shows the continuous cooling transformation diagram for a 1.13 wt% C iron-carbon alloy. Make a copy of this figure and then sketch and label continuous cooling curves to yield the following
Cite two important differences between continuous cooling transformation diagrams for plain carbon and alloy steels.
Briefly explain why there is no bainite transformation region on the continuous cooling transformation diagram for an iron–carbon alloy of eutectoid composition.
Name the micro structural products of 4340 alloy steel specimens that are first completely transformed to austenite, then cooled to room temperature at the following rates:(a) 10°C/s,(b) 1°C/s,(c)
Briefly describe the simplest continuous cooling heat treatment procedure that would be used in converting a 4340 steel from one microstructure to another.(a) (Martensite + bainite) to (ferrite +
On the basis of diffusion considerations, explain why fine pearlite forms for the moderate cooling of austenite through the eutectoid temperature, whereas coarse pearlite is the product for

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