1. CHAPTER 14: SYNTHESIS, FABRICATION, AND PROCESSING OF MATERIALS
ISSUES TO ADDRESS...
• What are the common fabrication techniques for metals?
How do the properties vary throughout a piece of metal that
has been quenched?
How can properties be modified by a post heat treatment?
How is the processing of ceramics different than for metals? 1

2. REFINEMENT OF STEEL FROM ORE2

3. METAL FABRICATION METHODS-I
FORMING
• Forging
(wrenches, crankshafts)
• Rolling
(I-beams, rails)
often at
elev. T
Adapted from Fig. 11.7, Callister 6e.
• Drawing
(rods, wire, tubing)
• Extrusion
(rods, tubing) 3

4. FORMING TEMPERATURE • Hot working --recrystallization • Cold working
--less energy to deform
--oxidation: poor finish
--lower strength
• Cold working
--recrystallization
--less energy to deform
--oxidation: poor finish
--lower strength
• Cold worked microstructures
--generally are very anisotropic!
--Forged
--Swaged
--Fracture resistant!
(a)
(b)
(c)
Reprinted w/ permission from R.W. Hertzberg, "Deformation and Fracture Mechanics of Engineering Materials", (4th ed.), John Wiley and Sons, Inc., (a) Fig. 10.5, p. 410 (micrograph courtesy of G. Vander Voort, Car Tech Corp.); (b) Fig. 10.6(b), p. 411 (Orig. source: J.F. Peck and D.A. Thomas,
Trans. Metall. Soc. AIME, 1961, p. 1240); (c) Fig , p. 415 (Orig. source: A.J. McEvily, Jr.
and R.H. Bush, Trans. ASM 55, 1962, p. 654.) 7

5. METAL FABRICATION METHODS-II
CASTING
• Sand Casting
(large parts, e.g.,
auto engine blocks)
• Die Casting
(high volume, low T alloys)
• Continuous Casting
(simple slab shapes)
• Investment Casting
(low volume, complex shapes
e.g., jewelry, turbine blades)
plaster
die formed
around wax
prototype 5

6. METAL FABRICATION METHODS-III
JOINING
• Powder Processing
(materials w/low ductility)
• Welding
(when one large part is
impractical)
Adapted from Fig. 11.8, Callister 6e.
(Fig from Iron Castings Handbook, C.F. Walton and T.J. Opar (Ed.), 1981.)
• Heat affected zone:
(region in which the
microstructure has been
changed). 6

7. THERMAL PROCESSING OF METALS
Annealing: Heat to Tanneal, then cool slowly.
Based on discussion in Section 11.7, Callister 6e. 7

8. HARDENABILITY--STEELS
• Ability to form martensite
• Jominy end quench test to measure hardenability.
Adapted from Fig , Callister 6e. (Fig adapted from A.G. Guy, Essentials of Materials Science, McGraw-Hill Book Company, New York, 1978.)
• Hardness versus distance from the quenched end.
Adapted from Fig , Callister 6e. 8

9. WHY HARDNESS CHANGES W/POSITION
• The cooling rate varies with position.
Adapted from Fig , Callister 6e.
(Fig adapted from H. Boyer (Ed.) Atlas of Isothermal Transformation and Cooling Transformation Diagrams, American Society for Metals, 1977, p. 376.) 9

10. HARDENABILITY VS ALLOY CONTENT
• Jominy end quench
results, C = 0.4wt%C
Adapted from Fig , Callister 6e.
(Fig adapted from figure furnished courtesy Republic Steel Corporation.)
• "Alloy Steels"
(4140, 4340, 5140, 8640)
--contain Ni, Cr, Mo
(0.2 to 2wt%)
--these elements shift
the "nose".
--martensite is easier
to form. 13

11. QUENCHING MEDIUM & GEOMETRY
• Effect of quenching medium:
Medium
air
oil
water
Severity of Quench
small
moderate
large
Hardness
small
moderate
large
• Effect of geometry:
When surface-to-volume ratio increases:
--cooling rate increases
--hardness increases
Position
center
surface
Cooling rate
small
large
Hardness
small
large 11

12. PREDICTING HARDNESS PROFILES
• Ex: Round bar, 1040 steel, water quenched, 2" diam.
Adapted from Fig , Callister 6e. 12

13. CERAMIC FABRICATION METHODS-I
GLASS
FORMING
• Pressing:
• Fiber drawing:
• Blowing:
Adapted from Fig. 13.7, Callister, 6e. (Fig is adapted from C.J. Phillips, Glass: The Miracle Maker, Pittman Publishing Ltd., London.) 13

14. GLASS STRUCTURE • Basic Unit: • Glass is amorphous
• Amorphous structure
occurs by adding impurities
(Na+,Mg2+,Ca2+, Al3+)
• Impurities:
interfere with formation of
crystalline structure.
• Quartz is crystalline
SiO2:
(soda glass)
Adapted from Fig , Callister, 6e. 14

15. GLASS PROPERTIES • Specific volume (1/r) vs Temperature (T):
• Crystalline materials:
--crystallize at melting temp, Tm
--have abrupt change in spec.
vol. at Tm
• Glasses:
--do not crystallize
--spec. vol. varies smoothly with T
--Glass transition temp, Tg
Adapted from Fig. 13.5, Callister, 6e.
• Viscosity:
--relates shear stress &
velocity gradient:
--has units of (Pa-s) 15

16. GLASS VISCOSITY VS T AND IMPURITIES
• Viscosity decreases with T
• Impurities lower Tdeform
Adapted from Fig. 13.6, Callister, 6e.
(Fig is from E.B. Shand, Engineering Glass, Modern Materials, Vol. 6, Academic Press, New York, 1968, p. 262.) 16

17. HEAT TREATING GLASS • Annealing: • Tempering:
--removes internal stress caused by uneven cooling.
• Tempering:
--puts surface of glass part into compression
--suppresses growth of cracks from surface scratches.
--sequence:
--Result: surface crack growth is suppressed. 17

18. CERAMIC FABRICATION METHODS-IIA
PARTICULATE
FORMING
• Milling and screening: desired particle size
• Mixing particles & water: produces a "slip"
• Form a "green" component
--Hydroplastic forming:
extrude the slip (e.g., into a pipe)
Adapted from Fig. 11.7, Callister 6e.
--Slip casting:
Adapted from Fig , Callister 6e.
(Fig is from W.D. Kingery, Introduction to Ceramics, John Wiley and Sons, Inc., 1960.)
solid component
hollow component
• Dry and Fire the component 18

19. FEATURES OF A SLIP • Clay is inexpensive • Adding water to clay
--allows material to shear easily
along weak van der Waals bonds
--enables extrusion
--enables slip casting
• Structure of
Kaolinite Clay:
Adapted from Fig , Callister 6e.
(Fig is adapted from W.E. Hauth, "Crystal Chemistry of Ceramics", American Ceramic Society Bulletin, Vol. 30 (4), 1951, p. 140.) 13

20. DRYING AND FIRING • Drying: layer size and spacing decrease. • Firing:
Adapted from Fig , Callister 6e.
(Fig is from W.D. Kingery, Introduction to Ceramics, John Wiley and Sons, Inc., 1960.)
• Firing:
--T raised to ( C)
--vitrification: glass forms from clay and flows between
SiO2 particles.
Adapted from Fig , Callister 6e.
(Fig is courtesy H.G. Brinkies, Swinburne University of Technology, Hawthorn Campus, Hawthorn, Victoria, Australia.) 20

21. CERAMIC FABRICATION METHODS-IIB
PARTICULATE
FORMING
• Sintering: useful for both clay and non-clay compositions.
• Procedure:
--grind to produce ceramic and/or glass particles
--inject into mold
--press at elevated T to reduce pore size.
• Aluminum oxide powder:
--sintered at 1700C
for 6 minutes.
Adapted from Fig , Callister 6e.
(Fig is from W.D. Kingery, H.K. Bowen, and D.R. Uhlmann, Introduction to Ceramics, 2nd ed., John Wiley and Sons, Inc., 1976, p. 483.) 21

22. CERAMIC FABRICATION METHODS-III
CEMENTATION
• Produced in extremely large quantities.
• Portland cement:
--mix clay and lime bearing materials
--calcinate (heat to 1400C)
--primary constituents:
tri-calcium silicate
di-calcium silicate
• Adding water
--produces a paste which hardens
--hardening occurs due to hydration (chemical reactions
with the water).
• Forming: done usually minutes after hydration begins. 22

23. SUMMARY • Fabrication techniques for metals Forming, casting, joining
Hardenability
Increases with alloy content
Fabrication techniques for ceramics
Glass forming (impurities affect forming temp.)
Particulate forming (needed if ductility is limited)
Cementation (large volume, room T process)
Heat treating: used to
Alleviate residual stress from cooling
Produce fracture-resistant components by putting
surface in compression 23

24. ANNOUNCEMENTS
Reading:
Core Problems:
Self-help Problems: