Callister - An introduction - 8th edition

Design Problems • 449
and tempering (Sections 10.5, 10.6, and 10.8)
with regard to the following:
(a) The total heat treatment procedure
(b) The microstructures that develop
(c) How the mechanical properties change
during the several heat treatment stages
11.31 What is the principal difference between
natural and artificial aging processes?
DESIGN PROBLEMS
Ferrous Alloys
Nonferrous Alloys
11.D1 The following is a list of metals and alloys:
Plain carbon steel Magnesium
Brass
Zinc
Gray cast iron
Tool steel
Platinum
Aluminum
Stainless steel
Tungsten
Titanium alloy
Select from this list the one metal or alloy
that is best suited for each of the following
applications, and cite at least one reason for
your choice:
(a) The block of an internal combustion engine
(b) Condensing heat exchanger for steam
(c) Jet engine turbofan blades
(d) Drill bit
(e) Cryogenic (i.e., very low temperature)
container
(f) As a pyrotechnic (i.e., in flares and fireworks)
(g) High-temperature furnace elements to
be used in oxidizing atmospheres
11.D2 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: (a) compositions
of some of the common metallic glasses, (b)
characteristics of these materials that make
them technologically attractive, (c) characteristics
that limit their utilization, (d) current
and potential uses, and (e) at least one
technique that is used to produce metallic
glasses.
11.D3 Of the following alloys, pick the one(s) that
may be strengthened by heat treatment,
cold work, or both: R50250 titanium,AZ31B
magnesium, 6061 aluminum, C51000 phosphor
bronze, lead, 6150 steel, 304 stainless
steel, and C17200 beryllium copper.
11.D4 A structural member 100 mm (4 in.) long
must be able to support a load of 50,000 N
(11,250 lb f ) without experiencing any plastic
deformation. Given the following data
for brass, steel, aluminum, and titanium,
rank them from least to greatest weight in
accordance with these criteria.
Alloy Yield Strength [MPa (ksi)] Density (g/cm 3 )
Brass 415 (60) 8.5
Steel 860 (125) 7.9
Aluminum 310 (45) 2.7
Titanium 550 (80) 4.5
11.D5 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: tin, tungsten, aluminum
alloys, magnesium alloys, and a 4140
steel.
Heat Treatment of Steels
11.D6 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 following alloys will satisfy
these requirements: 1040, 5140, 4340,
4140, and 8640? Justify your choice(s).
11.D7 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, 8640, 8630, and
8620, which will qualify if the quenching
medium is (a) moderately agitated water
and (b) moderately agitated oil? Justify
your choice(s).