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physics
thermodynamics

Questions and Answers of Thermodynamics

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 E (alloy) = EαVα + EβVβ (9.24) where E represents a specific property (modulus of elasticity, hardness, etc.),
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
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
Given here are the solidus and liquidus temperatures for the germanium-silicon system. Construct the phase diagram for this system and label each region.
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
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 α phase of composition 37 wt% Ni-63 wt% Cu? If so, what
Name the two stages involved in the formation of particles of a new phase. Briefly describe each.
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
(a) From the curves shown in Figure 10.11 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
Determine values for the constants n and k (Equation 10.17) for the recrystallization of copper 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 super cooling. (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 10.22), specify the nature of the final microstructure (in terms of micro constituents present
Make a copy of the isothermal transformation diagram for an iron-carbon alloy of eutectoid composition (Figure 10.22) and then sketch and label time-temperature paths on this diagram to produce the
(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
Using the isothermal transformation diagram for a 0.45 wt% C steel alloy (Figure 10.39), determine the final microstructure (in terms of just the micro constituents present) of a small specimen that
For parts (a), (c), (d), (f), and (h) of Problem 10.20, determine the approximate percentages of the micro constituents that form.Problem 10.20(a) Rapidly cool to 250°C (480°F), hold for 103 s,
Make a copy of the isothermal transformation diagram for a 0.45 wt% C iron-carbon alloy (Figure 10.39), and then sketch and label on this diagram the time-temperature paths to produce the following
Name the micro structural 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 10.40 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
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)
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
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
Briefly explain why fine pearlite is harder and stronger than coarse pearlite, which in turn is harder and stronger than spheroidite.
Cite two reasons why martensite is so hard and brittle.
Rank the following iron-carbon alloys and associated microstructures from the highest to the lowest tensile strength: (a) 0.25 wt%C with spheroidite, (b) 0.25 wt%C with coarse pearlite, (c) 0.60 wt%C
Briefly explain why the hardness of tempered martensite diminishes with tempering time (at constant temperature) and with increasing temperature (at constant tempering time).
Briefly describe the simplest heat treatment procedure that would be used in converting a 0.76 wt% C steel from one microstructure to the other, as follows: (a) Spheroidite to tempered martensite (b)
(a) Briefly describe the micro structural difference between spheroidite and tempered martensite. (b) Explain why tempered martensite is much harder and stronger.
Estimate the Rockwell harnesses for specimens of an iron-carbon alloy of eutectoid composition that have been subjected to the heat treatments described in parts (b), (d), (f), (g), and (h) of
Estimate the Brinell harnesses for specimens of a 0.45 wt% C iron-carbon alloy that have been subjected to the heat treatments described in parts (a), (d), and (h) of Problem 10.20. Problem 10.20 (a)
Determine the approximate tensile strengths for specimens of a eutectoid iron-carbon alloy that have experienced the heat treatments described in parts (a) and (c) of Problem 10.23. Problem 10.23 (a)
For a eutectoid steel, describe isothermal heat treatments that would be required to yield specimens having the following Rockwell hardnesses: (a) 93 HRB, (b) 40 HRC, and (c) 27 HRC.
(a) For the solidification of iron, calculate the critical radius r* and the activation free energy ΔG* 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
Is it possible to produce an iron-carbon alloy of eutectoid composition that has a minimum hardness of 90 HRB and a minimum ductility of 35%RA? If so, describe the continuous cooling heat treatment
Is it possible to produce an iron-carbon alloy that has a minimum tensile strength of 690 MPa (100,000 psi) and a minimum ductility of 40%RA? If so, what will be its composition and microstructure
It is desired to produce an iron-carbon alloy that has a minimum hardness of 175 HB and a minimum ductility of 52%RA. Is such an alloy possible? If so, what will be its composition and microstructure
(a) For a 1080 steel that has been water quenched, estimate the tempering time at 425°C (800°F) to achieve a hardness of 50 HRC. (b) What will be the tempering time at 315°C (600°F) necessary to
An alloy steel (4340) is to be used in an application requiring a minimum tensile strength of 1380 MPa (200,000 psi) and a minimum ductility of 43%RA. Oil quenching followed by tempering is to be
Is it possible to produce an oil-quenched and tempered 4340 steel that has a minimum yield strength of 1400 MPa (203,000 psi) and a ductility of at least 42%RA? If this is possible, describe the
(a) List the four classifications of steels. (b) For each, briefly describe the properties and typical applications.
Why must rivets of a 2017 aluminum alloy be refrigerated before they are used?
What is the chief difference between heat-treatable and non-heat-treatable alloys?
Give the distinctive features, limitations, and applications of the following alloy groups: titanium alloys, refractory metals, super alloys, and noble metals.
Cite advantages and disadvantages of hot working and cold working.
(a) Cite advantages of forming metals by extrusion as opposed to rolling. (b) Cite some disadvantages.
List four situations in which casting is the preferred fabrication technique.
Compare sand, die, investment, lost foam, and continuous casting techniques.
If it is assumed that, for steel alloys, the average cooling rate of the heat-affected zone in the vicinity of a weld is 10°C/s, compare the microstructures and associated properties that will
In your own words describe the following heat treatment procedures for steels and, for each, the intended final microstructure: full annealing, normalizing, quenching, and tempering.
(a) Cite three reasons why ferrous alloys are used so extensively. (b) Cite three characteristics of ferrous alloys that limit their utilization.
Cite three sources of internal residual stresses in metal components. What are two possible adverse consequences of these stresses?
Give the approximate minimum temperature at which it is possible to austenitize each of the following iron-carbon alloys during a normalizing heat treatment: (a) 0.20 wt% C, (b) 0.76 wt% C, and (c)
Give the approximate temperature at which it is desirable to heat each of the following iron-carbon alloys during a full anneal heat treatment: (a) 0.25 wt% C, (b) 0.45 wt% C, (c) 0.85 wt% C, and (d)
What is the purpose of a spheroidizing heat treatment? On what classes of alloys is it normally used?
Briefly explain the difference between hardness and harden ability.
What influence does the presence of alloying elements (other than carbon) have on the shape of a harden ability curve? Briefly explain this effect.
How would you expect a decrease in the austenite grain size to affect the harden ability of a steel alloy? Why?
Construct radial hardness profiles for the following:(a) A 50-mm (2-in.) diameter cylindrical specimen of an 8640 steel alloy that has been quenched in moderately agitated oil(b) A 75-mm (3-in.)
Compare the effectiveness of quenching in moderately agitated water and oil by graphing, on a single plot, radial hardness profiles for 65-mm (2 1/2-in.) diameter cylindrical specimens of an 8630
Compare precipitation hardening (Section 11.9) and the hardening of steel by quenching and tempering (Sections 10.5, 10.6, and 10.8) with regard to (a) The total heat treatment procedure (b) The
Compute the volume percent of graphite VGr in a 3.5 wt% C cast iron, assuming that all the carbon exists as the graphite phase. Assume densities of 7.9 and 2.3 g/cm3 for ferrite and graphite,
Compare gray and malleable cast irons with respect to (a) Composition and heat treatment, (b) Microstructure, and (c) Mechanical characteristics.
Compare white and nodular cast irons with respect to (a) Composition and heat treatment, (b) Microstructure, and (c) Mechanical characteristics.
Is it possible to produce malleable cast iron in pieces having large cross-sectional dimensions? Why or why not?
What is the principal difference between wrought and cast alloys?
Below is a list of metals and alloys:Plain carbon steelMagnesiumBrassZincGray cast ironTool steelPlatinumAluminumStainless steelTungstenTitanium alloySelect from this list the one metal or alloy that
A cylindrical piece of 4140 steel is to be austenitized and quenched in moderately agitated oil. If the microstructure is to consist of at least 50% martensite throughout the entire piece, what is
A cylindrical piece of 8640 steel is to be austenitized and quenched in moderately agitated oil. If the hardness at the surface of the piece must be at least 49 HRC, what is the maximum allowable
Is it possible to temper an oil-quenched 4140 steel cylindrical shaft 100 mm (4 in.) in diameter so as to give a minimum tensile strength of 850 MPa (125,000 psi) and a minimum ductility of 21%EL? If
Is it possible to temper an oil-quenched 4140 steel cylindrical shaft 12.5 mm (0.5 in.) in diameter so as to give a minimum yield strength of 1000 MPa (145,000 psi) and a minimum ductility of 16%EL?
Copper-rich copper-beryllium alloys are precipitation hardenable. After consulting the portion of the phase diagram (Figure 11.30), do the following: (a) Specify the range of compositions over which
A solution heat-treated 2014 aluminum alloy is to be precipitation hardened to have a minimum tensile strength of 450 MPa (65,250 psi) and a ductility of at least 15%EL. Specify a practical
Is it possible to produce a precipitation-hardened 2014 aluminum alloy having a minimum tensile strength of 425 MPa (61,625 psi) and a ductility of at least 12%EL? If so, specify the precipitation
A group of new materials are the metallic glasses (or amorphous metals). Write an essay about these materials in which you address the following issues: (1) Compositions of some of the common
Of the following alloys, pick the one(s) that may be strengthened by heat treatment, cold work, or both: R50500 titanium, AZ31B magnesium, 6061 aluminum, C51000 phosphor bronze, lead, 6150 steel, 304
A structural member 100 mm (4 in.) long must be able to support a load of 50,000 N (11,250 lbf) without experiencing any plastic deformation. Given the following data for brass, steel, aluminum, and
Discuss whether it would be advisable to hot work or cold work the following metals and alloys on the basis of melting temperature, oxidation resistance, yield strength, and degree of brittleness:
A cylindrical piece of steel 25 mm (1.0 in.) in diameter is to be quenched in moderately agitated oil. Surface and center hardnesses must be at least 55 and 50 HRC, respectively. Which of the
A cylindrical piece of steel 75 mm (3 in.) in diameter is to be austenitized and quenched such that a minimum hardness of 40 HRC is to be produced throughout the entire piece. Of the alloys 8660,
A cylindrical piece of steel 38 mm (1 1/2in.) in diameter is to be austenitized and quenched such that a microstructure consisting of at least 80% martensite will be produced throughout the entire
A cylindrical piece of steel 90 mm (3 1/2 in.) in diameter is to be quenched in moderately agitated water. Surface and center hardnesses must be at least 55 and 40 HRC, respectively. Which of the
For a ceramic compound, what are the two characteristics of the component ions that determine the crystal structure?
Iron sulfide (FeS) may form a crystal structure that consists of an HCP arrangement of S2 ions. (a) Which type of interstitial site will the Fe2+ ions occupy?
Magnesium silicate, Mg2SiO4, forms in the olivine crystal structure that consists of an HCP arrangement of O2- ions. (a) Which type of interstitial site will the Mg2+ ions occupy? Why? (b) Which type
Using the Molecule Definition Utility found in both "Metallic Crystal Structures and Crystallography" and "Ceramic Crystal Structures" modules of VMSE, located on the book's web site

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