Martienssen W., Warlimont H. (Eds.). Handbook of Condensed Matter and Materials Data

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352 Part 3 Classes of Materials

4.10

4.00

3.90

3.80

3.70

3.60

3.50

100

Nickel (at. %)

200

Lattice spacing, kX Vacant lattice sites (%)

Fig. 3.1-225 Vacant lattice sites in Au

−

Ni alloys [1.225,

p. 141]

Mechanical Properties

The mechanical properties of gold are given

in Tables 3.1-170–3.1-176 and Figs. 3.1-226–

3.1-237 [1.216, 217]. References for data of elastic

constants of Au alloys are given in [1.217]. Pure gold is

very soft. It can be cold-worked to more than 90% by

Table 3.1-170 Modulus of elasticity of Au in crystal direc-

tions (GPa) [1.217, p. 208]

E 100 E 110 E 111

42 81 114

Table 3.1-171 Elastic constants of Au (GPa) [1.217, p. 209]

T (

◦

C) c11 c12 c14

−273 131.4 97.3 51.1

20 124.0 93.4 46.1

Table 3.1-172 Mechanical properties of Au (99.99%) at

different temperatures [1.217, p. 209]

T (

◦

C) E (GPa) R

(MPa) R

p0.2

(MPa) HV

20 79 125 30 28

200 75 110 20 19

400 70 92 − 16

700 58 40 − 5

E = Modul of elasticity, R

= Tensile strength, R

= Limit of

proportionality, HV = Vickers hardness

Table 3.1-176 Mechanical properties of AuPt alloys in an-

nealed and aged condition, Pt in wt% [1.217, p. 211]

Table 3.1-173 Tensile strength R

(MPa)ofbinaryAu

alloys [1.217, p. 210]

Content (wt%) 2 5 10 20

Alloying element

Ag 140 150 170 190

Co 240 − − −

Cr 200 − − −

Cu 190 290 400 500

Fe 190 − − −

Ni 220 350 470 680

Pd 150 170 220 290

Pt 150 189 240 370

Table 3.1-174 Mechanical properties of Au (99.99%) as

a function of the reduction V (%) in thickness by cold

forming [1.217, p. 209]

V (%) R

(MPa) A (%) HV

0 120 45 28

10 140 22 55

30 180 75 63

50 220 4 65

= Tensile strength, A = Elongation of rupture,

HV = Vickers hardness

Table 3.1-175 Change of hardness (HV 10) of Au alloys by

cold forming(Degree ofreduction in thickness in %)[1.217,

p. 210]

Degree of reduction 0 40 80

in thickness (%)

Alloying element

Ag20 40 95 1141

Ag25Cu5 92 160 188

Ag20Cu10 120 190 240

Co5 92 126 154

Ni5 120 162 188

Pt10 78 102 118

Pd30Cu5 92 174 216

Alloy R

(MPa) A (%) HV

Pt10

250 38 42

Pt30

430 12 120

Pt30

740 − 300

Pt50

900 3 240

Pt50

1460 2 420

annealed at 1000–11 150

◦

C and quenched

stored 70 h at 500

◦

stored 25 h at 500

◦

Part 3 1.10

Metals 1.10 Noble Metals and Noble Metal Alloys 353

140

120

100

020406080100

(at. %)

E ( GPa)

1–x

Fig. 3.1-226 Modulus of elasticity of Au

−

Cu and Au

−

alloys [1.217, p. 219]

Fig. 3.1-227 Inﬂuence of alloying elements on the hardness

of binary Au alloys [1.217, p. 211]

4 ×10

0 20 40 60 80 100

Concentration (at. %)

3 ×10

(kp/mm

)

2 ×10

1 ×10

Young’s modulus

Fig. 3.1-228 Modulus of elasticity versus composition of

binary noble-metal alloys [1.216, p. 77]

rolling or drawing. Cold hard drawn wires (about 90%

deformation) have predominantly 111 ﬁber texture,

which is converted by annealing into 100 orienta-

tion [1.249]. Strengthening of pure gold is affected by

alloying (solid solution hardening, precipitation harden-

ing) or by dispersion hardening. Ternary Au

−

Fig. 3.1-229a,b Hardness of Au

−

Co alloys by annealing;

(a) inﬂuence of time, (b) inﬂuence of temperature T [1.231,

p. 62]

200

010 30

X (wt %)

150

100

Hardness (HV)

1–x

Ni Ge

Au + 0.3% Co + 0.05% Mo

Au + 0.3% Co

+ 0.03% Mo

Au + 0.3% Co

100

0 100 700

Temperature (°C)

100

0 1 300

Time (h)

200 300 400 500 600

5 10 50 100

Vickers hardness HV

0.5

Vickers hardness HV

0.5

Au + 0.5% Co

Au + 0.1% Co

Au + 0.3% Co

Au + 0.5% Co

Part 3 1.10

354 Part 3 Classes of Materials

440

400

360

320

280

240

200

160

6020 40 0 6020 4006020 40

Precipitation time (minutes)

Vickers hardness HV

650 °C

700 °C

750 °C

Fig. 3.1-230 Precipitation hardening of Au/Pt-40 (solid curve) and Au/Pt-50 (broken curve): solution treatment 15 min

at a) 950

◦

C, b) 1050

◦

C and c) 1150

◦

C. Precipitation hardening performed at 650

◦

C, 700

◦

C, and 750

◦

C [1.218, p. 610]

200

0.1 1 1000

Heat treatment time (h)

150

100

10 100

Hardness HV10

400°C

500°C

600°C

Fig. 3.1-231 Precipitation-hardening characteristic of Au-

1% Ti alloy by annealing [1.252, p. 139]

160

140

120

100

–1

Ageing time

Hardness HV

After 70% reduction

After 25% reduction

After solution

annealing

80 20

Ag 80 60 40 20 Cu

wt %

150

140

130

120

110

100

Fig. 3.1-232 Hardness of annealed and quenched Au

−

Cu alloys [1.253, p. 517]

alloys can be hardened by decomposition into Cu-rich

−

Au and Ag-rich Ag

−

Au phases during annealing

below the critical temperature of the miscibility gap and

Fig. 3.1-233 Hardness of the alloy AuSb0.3Co0.2as

a function of the reduction in thickness and of annealing

time [1.254, p. 49]

Part 3 1.10

Metals 1.10 Noble Metals and Noble Metal Alloys 355

010

100

Copper content (wt%)

200

Tensile strength (kg/mm

Elongation (%)

Vickers

hardness (HV)

Tensile strength

(75%worked)

Hardness

(75% worked)

Elongation

(as annealed)

Hardness

(as annealed)

Tensile

strength

(as annealed)

Elongation

(75 % worked)

Fig. 3.1-235 Tensile strength and hardness of 18 carat

−

Cu alloys as a function of Cu content [1.218,

p. 437]

200

150

100

Copper content (wt %)

20 40 60

Brinell hardness (HB)

Age-hardened 300° C

Solution treatment

K18

K10

K14

Fig. 3.1-236 Inﬂuence of Cu content on age hardening of

14 carat and 18 carat Au

−

Cu alloys [1.218, p. 437]

by formation of the ordered Au

−

Cu-phase at more than

75 wt% Au. Hardening of Au by alloying with rare-earth

metals is described in detail in [1.248]. Grain reﬁne-

ment, applied especially to jewelry and dentistry alloys,

is affected by the addition of 0.05–1at.%ofIr,Ru,or

Co [1.250,251].

0 20 100

Cold work (%)

600

500

400

300

200

100

110

40 60 80

700

600

500

400

300

100

140

120

100

10 200 40

1000

800

700

600

500

300

210

170

150

130

110

10 400 90

60 900 190

Elongation

δ (%)

Tensile

strength

(N/mm

)

Vickers

hardness

HV 10

HV10

Fig. 3.1-234a–c Mechanical properties of (a) Au, (b) AuAg30,

and

(%) [1.231, p. 58f.]

Part 3 1.10

356 Part 3 Classes of Materials

350

0 10 60

Silver (%)

20 30 0 10 20 4030 0 10 20 4030 50

300

250

200

150

100

Silver (%)Silver (%)

18 carat, 17% Au 14 carat, 58.3% Au 10 carat, 41.7% Au

Aged

Quenched

Aged

Air

cooled

Quenched

Aged

Air

cooled

Quenched

Hardness (HV)

Variation of hardness with silver content for copper alloys

Fig. 3.1-237 Variation of hardness with silver content for Au

−

Cu alloys [1.217]

Electrical Properties

Tables 3.1-177–3.1-179 and Figs. 3.1-238, 3.1-239

[1.217, 231, 255] summarize the electrical properties of

gold and gold alloys. The residual resistivity ratio for

high purity gold amounts to 300. The electrical conduc-

tivity of gold alloys decreases in the low concentration

range roughly linearly with the atomic concentration of

Table 3.1-177 Speciﬁc electrical resistivity ρ =ρ

+ρ

(T ) of Au at different temperatures (ρ

= 0.0222 µΩ cm) [1.217,

p. 157]

T (K) 20 60 120 273.2 400 800 1000 1200

ρ(µΩ cm) 0.0138 0.287 0.796 2.031 3.094 6.742 8.871 11.299

at T < 400 K, ρ

= 0.014 µΩ cm at T > 400 K

Table 3.1-178 Speciﬁc electrical resistivity (ρ

) and temperature coefﬁcient of resistivity (TCR) of Au

−

Pd and Au

−

alloys [1.217, p. 158]

Solute Content

Content 80

60 40 30

Pd ρ

9.8 17 30 26

TCR

0.88 0.61 0.45 1.2

Pt ρ

28 44 37 34

TCR

0.28 0.26 0.82 0.8

TCR

−ρ

−T

the solute. Au alloys with 1.15 at.% Mn show increas-

ing temperature coefﬁcients of the electrical resistivity

(positive TCR) due to the Kondo effect. This behavior

is applied in resistance thermometers for temperature

measurements below 20 K. Superconductivity occurs in

intermetallic phases of Au

−

Ge with 2.99 < T

< 3.16 K

and Au

−

Sn with T

= 1.25 K [1.256, 257].

Part 3 1.10

Metals 1.10 Noble Metals and Noble Metal Alloys 357

Table 3.1-179 Increase of atomic electrical resistivity of Au

by alloying elements ∆ρ/C (µΩ cm/at.%) [1.217, p. 157]

Base element Alloying elements ρ/C (µ cm/at.%)

Au Ag 0.35

Al 1.9

Cd 0.60

Co 6.2

Cr 4.5

Cu 0.4

Fe 8

Ga 2.2

Ge 5.5

Hg 0.4

In 1.4

Mn 2.4

Mo 4

Ni 0.8

Pb 3.9

Pt 1

Rh 3.3

Ru 1.6

Sn 3.5

Ti 13

V 13

Zn 0.94

Alloying addition (at. %)

468

Electrical conductivity σ

(µΩ cm)

10 100

(at. %) Au

0 2030405060708090

Electrical conductivity σ (10

–4

Ωcm)

AuCu

20 °C

500 °C500 °C

20 °C

Fig. 3.1-238 Speciﬁc electrical conductivity of Au

−

Cu al-

loy phases [1.255, p. 619]

Fig. 3.1-239 Inﬂuence of alloying elements on the electric-

al conductivity of binary Au alloys [1.231, p. 50]

Part 3 1.10

358 Part 3 Classes of Materials

Thermoelectric Properties

Tables 3.1-180–3.1-183 [1.216] and Figs. 3.1-240–

3.1-242 [1.216,218] list the thermoelectric properties

of gold and its alloys. Au

−

Fe and Au

−

Co-alloys

are used in thermocouples for measuring very low

temperatures [1.258], Au

−

Pd and Au

−

Pt al-

loys in thermocouples working under highly corrosive

conditions.

–5

–10

–15

Temperature (K)

01015

Thermal electromotive force (mV)

2.0 % Fe

0.5

0.1

0.002

0.004

0.02

Fig. 3.1-240 Thermal electromotive force of Au

−

Fe al-

loys [1.218, p. 58]

Table 3.1-180 Absolute thermoelectric power of gold [1.216, p. 94]

Temperature (

◦

C) −255 −200 −160 −100 0 100 300 500 700

Thermoelectr. power (µV/K) −0.93 −0.78 +0.80 +1.00 +1.1 +1.8 +3.1 +3.3 +3.7

Table 3.1-181 Thermal electromotive force E of Au and Pt (mV) at different temperatures; reference junction at

◦

C [1.216, p. 159]

T (

◦

C) −200 −100 −50 +100 +200 +400 +800

Au,Pt

(mV) −0.39 −0.21 −0.10 0.77 1.834 4.623 12.288

Table 3.1-182 Thermal electromotive force of Au

−

Fe and Au

−

Co-alloys [1.216, p. 100]

(K) T

(K) Au

−

2.1

Cu (at.%) Au

−

0.02

Cu (at.%)

4.2 10 0.044 0.093

20 0.173 0.208

4.2 40 0.590 0.423

Table 3.1-183 Thermocouples for very low temperatures [1.216, p. 97, 99]

• AuFe(0.03 at.% Fe)−chromel from 4.2 to 273 K

• AuCo(2.11 at.% Co)−AuAg (0.37 at.% Ag) or Cu from −240 to 0

◦

• AuFe(0.02 at.% Fe)−Cu from −270 to −230

◦

Magnetic Properties

Figure 3.1-243 [1.217] illustrates the metal’s magnetic

properties. Gold is diamagnetic. The magnetic suscep-

tibility remains constant from 0 K to the melting point.

Alloying of gold with B metals causes only weak varia-

tions compared to pure gold. In the range of continuous

solid solutions, the molar susceptibilities remain nega-

tive, the alloys are diamagnetic. Ni, Pd, and Pt dissolve

diamagnetically up to25 at.%. Cr, Fe, and Mngiverise to

paramagnetism. Magnetic transformations are reported

95 85

(wt%) Au

Thermal electromotive force E

A, Pt

(mV)

= 900 °C

=0°C

Fig. 3.1-241 Thermal electromotive force of Au al-

loys [1.216, p. 97]

Part 3 1.10

Metals 1.10 Noble Metals and Noble Metal Alloys 359

CuAg

50 wt %

50 wt %50 wt %

150 µv

200 µv

250 µv

150 µv

100 µv

Fig. 3.1-242 Thermal electromotive force of Au

−

alloys [1.216, p. 99]

for Au

−

Co alloys between ≈ 18 and 92 wt% Co at

1122

◦

CandforAu

−

Ni alloys between ≈ 3 and 95 wt%

at ≈340

◦

C [1.259].

Thermal Properties

Data for thermal expansion and thermal conductivity of

Au and Au alloys are listed in Tables 3.1-145–3.1-149.

Table 3.1-184 [1.217] shows the recrystallization tem-

peratures of gold of different purity. After 90% cold

work, the hardness decreases by about 50%.

Optical Properties

For the optical properties of colored Au alloys, see Ta-

bles 3.1-151, 3.1-152 and Figs. 3.1-244–3.1-247 [1.260–

263]. The reﬂectivity of gold shows a marked decrease

at ≈ 550 nm in the visible range with a minimum of

R ≈ 0.25 in the near ultraviolet. Interband transitions

occur at ≈2.17 eV. The reﬂected light contains all wave-

lengths above 550 nm, which accounts for the typical

gold color.

Table 3.1-184 Recrystallization temperatures of Au 3N,

4N and 5N purity [1.217, p. 210]

Purity (%) Decrease of hardness

50% 100%

recryst.

99.9(3N) 200

99.99 (4N) 160 200

99.999 (5N) 112 149

100

030

T (K)

510152025

a) χ

(10

–9

–1

)

Au-1 at% Fe

Au-0.5 at% Fe

3000

2500

2000

1500

1000

500

040

T (K)

5101520253035

600 K

0.94

0.06

295 K

80 K

b) χ

(10

–9

–1

)

Fig. 3.1-243a,b Magnetic susceptibility of (a) Au

−

Fe and

(b) Au

−

Co alloys [1.217, p. 169]

100

(µm)

2000 5000

3000 7500 (Å)

1.5 2 3 4 5 6 7 81

Wavelength

Visible spectrum

Reflectivity (%)

Fig. 3.1-244 Reﬂectance as a function of wavelength of

pure Au [1.260, p. 53]

Part 3 1.10

360 Part 3 Classes of Materials

100

20 100

Film thickness (µm)

40 60 800

Reflectance R, Transmission D (%)

Fig. 3.1-245 Reﬂectance and transmission of thin Au ﬁlms

at λ = 492 µm [1.260]

350 750

Wavelength (nm)

400 450 500 550 600 650 700

Reflectance (%)

AP10

AP5

Fig. 3.1-246 Reﬂectance-wavelength curves for Au

−

and binary Au

−

Pt alloys [1.261, p. 130]

Diffusion

Characteristic data are shown on Tables 3.1-153–

3.1-156, 3.1-158 and Figs. 3.1-212, and 3.1-248 [1.217,

238].

20 CuAg 40 60 80

22 ct

18 ct

14 ct

10 ct

8ct

Gold-yellow

wt %

Yellow

Green-yellow

Whitish Red

Reddish

Pale

greenish

yellow

Yello-

wish

Fig. 3.1-247 ColorrangesofAu

−

Cu alloys [1.262,

p. 37]

–10

–11

–12

–13

–14

–15

–16

–17

0.70

1.15

(10

–3

–1

) 1/T

0.850.75

0.80 0.90

0.95

1.00

1.05

1.10

1300 1200 1100 1000 900

T(K)

Tm = 1338 K Matrix: Au

D (m

–1

)

Fig. 3.1-248 Dif fusion of impurities in Au [1.238, p. 191]

Part 3 1.10

Metals 1.10 Noble Metals and Noble Metal Alloys 361

Chemical Properties

Figures 3.1-249 and 3.1-250 show that gold has the re-

duction potential of E

=+1.42 V for Au/Au

.At

room temperature it is resistant against dry and wet

atmospheres, H

O, O

, F, I, S, alkali, non-oxidizing

acids, and ozone below 100

◦

C. It is dissolved in 3 HCl+

1 HNO

,HCl+Cl

in acid concentration above 6 mol/l,

in NaCN/H

O/O

, and other oxidizing solutions. Halo-

gens generally attack gold, except for dry ﬂuorine belo w

300

◦

C. Gold alloys are corrosion-resistant against acids

if the base metal content is lower than 50% and also if

each base metal present contains more than 50% of no-

ble metal. Detailed information of chemical properties

of Au and Au alloys are given in [1.217].

Gold and gold alloys (with Ag, Ir, Pt) and cationic

gold (I) phosphines act as selective catalysts in hy-

drogenation, oxidation, and reduction reactions [1.264–

266]. Nanometer-sizedAu particles (≈5 nm) inthe pres-

ence of ceria or a transition-metal oxide have superior

catalytic activities [1.267–269, 269].

Special Alloys

Binary Alloys. The material Au–20 wt% Ag is used

for low-voltage electrical contacts. Gold–copper alloys

form the ordered phases Au

Cu [60748-60-9], AuCu

[12006-51-8], and AuCu

[12044-96-1]. Gold–nickel

alloys decompose into gold-rich and nickel-rich solid

200

0 750

Temperature (°C)

100

0.1

250 500

(mm a

–1

)

Fig. 3.1-249 Corrosion of gold in dry chlorine gas [1.217,

p. 183]

Ag 50

Gold (at. %)

10 20 30 40

Lifetime (s)

HNO

1.4 g/cm

FeCl

HNO

1.52 g/cm

Fig. 3.1-250 Lifetime of Ag

−

Au solid solutions in HNO

and FeCl

solution [1.217, p. 197]

solution phases in a miscibility gap below 800

◦

C. The

alloy Au–18 wt% Ni is a structural material for turbine

blades in jet engines and nuclear and space technology

materials.

Alloys of Au

−

Co(Fe, Ni) with 1–3 wt% Co, Fe,

or Ni serve as hard and wear-resistant surface coat-

ings on electrical contacts. The gold-cobalt alloy of

Au–5 wt% Co is resistant against silver migration.

The gold-platinum alloy of Au–10 wt% Pt is used

for electrical contacts working under highly corrosive

conditions. The high Pt content alloy Au–30 wt% Pt

serves as a material for spinnerets for rayon and as

a high-melting platinum solder (T

liquidus

= 1450

◦

solidus

= 1228

◦

C), additions ≈ 0.5% of Rh, Ru, or

Ir suppress segregation. Gold-Platinum alloys con-

taining 40 to 65 wt% Au harden by quenching from

1100

◦

C and annealing at 500

◦

C to yield strengths

up to ≈ 1400 N/mm

. Au–1 wt% Ti (Figs. 3.1-222,

3.1-231 [1.246, 252, 270, 271]) is of importance for

bonding wires, electrical conductors, and as hard high-

carat gold alloy for jewelry. Strengthening can be

induced by precipitation of the intermetallic compound

Ti and by formation of highly-dispersed Ti oxide

on annealing in an oxidizing atmosphere. The alloys

Au–12 wt% Ge, Au–3.1 wt% Si, and Au–20 wt% Sn are

low melting eutectic solders of high strength, corro-

sion resistance and stability against temperature cycling,

Part 3 1.10