Mg Pure Magnesium

Mg Pure Magnesium 1

Transitions, melting point mp = 650 °C [1].

2

Density (p) thermal expansion coefficient p

(solid) = 1740 kg m" [2] a = 30 x 10" K" [2]. 3

25

6

1

The density as a function of temperature is given in Figure 1 and Table 1. The density-temperature relation for liquid Mg recommended by Iida and Guthrie [3] is identical to that recommended by Watanabe et al [4] viz p ( k g . m ) ^1740 - 0.156 ( T - 2 5 ° C )

(1)

p

(2)

-3

s

( k g . m ) = 1590-0.26 ( T - 6 5 0 ° C ) -3

e

The density decrease at the melting point from the data shown in Table 1 is 3.1%. 1800 -j

1

h

200

400

3

Density, p (Kg m" )

1750

0 Figure J

3

600

Temperature (°C)

800

1000

1200

Density of liquid Mg as a function of temperature [3,4].

Heat capacity (C ) enthalpy (H -H ) p

x

25

Heat capacity and enthalpy as functions of temperature are given in Figures 2 and 3, respectively and Table 1. Dinsdale [1] reported the following values. AH* - 349 J g C (*) = 1.32Jg- K" 18

1

,

1

p

143

RECOMMENDED VALUES OF THERMOPHYSICAL PROPERTIES FOR SELECTED COMMERCIAL ALLOYS

p

1

1

:Capacity, C (Jg* K" )

1.35

»

1.05 200

1800

^A>

800

1000

1200

1

1

200

400

1

1

f-

L

1400 1200

3

*

600 Temperature (°C)

Heat capacity of pure Mg as a function of temperature.

Figure 2

1600

400

in

1000

CO JO «•"•» c LU

Figure 3 4

600 800 Temperature (°C)

1000

1200

Enthalpy (H -H ) of pure Mg as a function of temperature. x

25

Thermal conductivity (X) thermal diffusivity (a)

Thermal conductivity values have been reported by Touloukian et al [5]. These values are given in Table 1 and have been converted to thermal diffusivity values using the recommended values of C and density values (Table 1). Mills et al [6] recommended the following values: p

X™ = M S W m ^ K " : X? = 79Wm" K" 1

1

X = 79+7xl0" (T-650)Wm" K" 2

1

{

These are shown in Figure 4.

144

1

1

(3)

Mg

170 a

PURE M A G N E S I U M

h

Thermal Conductivity, X

160 --

70 -( 0

Figure 4

5

1

1

200

400

1

1

600 800 Temperature (°C)

1

1000

V 1200

Thermal conductivity of Mg as a function of temperature [6].

Viscosity (r|)

Lihl et al [7] have reported the viscosity measurements for pure Mg shown in Figure 5, with rf = 1.25 mPas.

Viscosity,N (mPas)

1.30 +

Temperature (°C)

Figure 5

6

Viscosity of liquid magnesium as a function of temperature [7].

Surface tension (y)

Keene [8] reviewed the measurements of surface tension reported for pure Mg and recommended the following relation (shown in Figure 6). yOnNm" ) = 577 - 0.26 (T - 650 °C) 1

145

(4)

1

Surface Tension, y (mN m" )

RECOMMENDED VALUES OF THERMOPHYSICAL PROPERTIES FOR SELECTED COMMERCIAL ALLOYS

600

Figure 6

7

650

700

750

800

850

Temperature (°C)

900

950

1000

1050

Surface tension of pure Mg as a function of temperature.

Emissivity

Shiraishi [9] reported values of z at 0.65 pm at 25 °C of 0.74 but with s decreasing rapidly with decreasing wavelength. Touloukian [5] also reported a hemispherical total emissivity value of 0.12 for a polished surface at temperatures between 70 and 200 °C. x

x

References 1.

Dinsdale, A T: SGTE data for pure elements. CALPHAD 15 (1991) 317/425.

2.

Touloukian, Y S: Thermophysical properties of high temperature solid Volume 1, Elements, publ. McMillan, New York (1967).

3.

Iida, T and Guthrie, R I L: The physical properties of liquid metals, Oxford Science Press, Oxford (1988).

4.

Watanabe, S; Ogino, K and Tsu, Y: Handbook of physico-chemical properties at high temperatures, edited Y Kawai and Y Shiraishi, publ. ISIJ, Tokyo (1988), Chapter 1.

5.

Touloukian, Y S; Powell, R W; Ho, C Y and Klemens P G: Thermophysicalproperties matter: Volume 1 Thermal conductivity, publ. IFI/Plenum, New York (1970).

6.

Mills, K C; Monaghan, B J and Keene, B J: Intl. Materials Review 41 (1996), 209-242.

7.

Lihl, P; Nachigall, E and Schwaiger, A: Z Metallic. 59 (1968) 213.

8.

Keene, B J: Intl. Mater. Reviews 38 (1993) 157/192.

9.

Shiraishi, Y: as in ref 1, Chapter 10.

146

materials:

of

Mg

PURE M A G N E S I U M

Table 1 Recommended values for thermophysical properties of pure Mg T

°C 25 100 200 300 400 500 600 650 650 700 800 900 1000 a

a

a

(H -H

PT

T

kgm1740 1728 1713 1697 1681 1666 1650 1642 1590 1577 1551 1525 1499

3

Jg" K" 1.025 1.06 1.11 1.16 1.19 1.24 1.30 1.32 1.32 1.32 1.32 1.32 1.32 1

1

2 5

Jg 0 78 187 300 418 540 667 733 1081 1213 1345 1477 1609 1

)

10" a m s 87 84 80 76 74 71 68 67 37 39 43.5 48 52

= melting point

147

X Win K 156 154 152 150 148 146 145 145 79 82 89 96 103 1

1

mPas

1.25 1.12 0.91 0.80

-

y

mNm

577 564 538 512 486

1

0.65 urn

0.59 0.59 0.59 0.59