1. 신소재개론 및 설계 (기초 2) ISSUES TO ADDRESS...
• How are metal alloys classified and how are they used?
• What are some of the common fabrication techniques? 1

2. 금속의 분류 Steels Cast Irons <1.4wt%C 3-4.5 wt%C Eutectic: Eutectoid:Fe 3 C
cementite
Metal(금속)
Steels
Ferrous(철)
Nonferrous(비철)
Cast Irons Cu Al Mg Ti
<1.4wt%C
3-4.5
wt%C
Steels
Cast Irons
<1.4wt%C
3-4.5
wt%C
T(°C)
1600 d L
1400 g +L
1200 g
L+Fe 3 C
1148°C
austenite
Eutectic:
1000
4.30 a g
+Fe 3 C + a
800 g
727°C
ferrite
Eutectoid: 6 00
0.77 a
+Fe 3 C 4 00 1 2 3 4 5 6
6.7
(Fe) C 2 o ,
wt% C

3. 강(STEELS) 3

4. 비철 합금 NonFerrous Alloys • Cu Alloys • Al Alloys • Mg AlloysB
rass
: Zn is subst. impurity
(costume jewelry, coins,
corrosion resistant)
Bronze
: Sn, Al, Si, Ni are
subst. impurity
(bushings, landing
gear)
Cu-Be :
precip. hardened
for strength
• Al Alloys
-lower r
: 2.7g/cm 3
-Cu, Mg, Si, Mn, Zn additions
-solid sol. or precip.
strengthened (struct.
aircraft parts
& packaging)
• Mg Alloys
-very low
: 1.7g/cm
-ignites easily -
aircraft, missles
• Refractory metals
-high melting T
-Nb, Mo, W, Ta
• Noble metals
-Ag, Au, Pt
oxid./corr. resistant
• Ti Alloys
: 4.5g/cm
vs 7.9 for steel
-reactive at high T
space applic. 4

5. 금속의 제조(제철) 5

6. 금속의 가공(포밍) FORMING • Forging (wrenches, crankshafts) • Rolling
(I-beams, rails)
often at
elev. T
• Drawing
(rods, wire, tubing)
• Extrusion
(rods, tubing) 6

7. 금속의 가공(주조) CASTING • Sand Casting • Die 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 8

8. 금속의 가공(용접) JOINING • Powder Processing • Welding
(materials w/low ductility)
• Welding
(when one large part is
impractical)
• Heat affected zone:
(region in which the
microstructure has been
changed). 9