COST 507 - Repositório Aberto da Universidade do Porto

4.2 Thermal conductivity of industrial Al­Si­alloys
Thermal conductivity results of selected Al­Si­alloys are presented at Fig.3. For alloys with
varying Si­content and constant amount of other elements the almost linear decreasing of
thermal conductivity with increasing of Si has been observed (ca. 2 Wrrï'K" 1 per each weight
% of Si). It is caused by the low solubility of Si in the ΑΙ­matrix and its precipitation as free
silicon. Copper builds with aluminium the intermetallic compound AI 2 Cu and its Influence on
thermal conductivity is more intensive: thermal conductivity of KS1295 (4%Cu) is 16% lower
then KS1275 (1%Cu).
170
­­G­ •KS1275.1
...·· •KS1275
­Q· •KS281.1
_.^. ■KS1295
!
■·.·.%, >
100 150 200 250 300 350
Temperature [°C ]
450 500
Fig.3 Thermal conductivity of Al­Si­based industrial alloys
The influence of the thermal treatment on the thermal conductivity can be observed in Fig.4.
Specimens of alloy KS1295 were aged at different conditions (time and temperature)
resulting in different hardness of the material. Investigations of thermal conductivity and
hardness as a function of a temperature and time [96Jar/Rei] allowed us to find a correlation
between the both properties for the examined alloys (Flg.5). Three curves obtained for
KS1295 at 100, 250 and 300°C show approximately a linear correlation between thermal
conductivity and hardness up to 150HB. The slope of the curves decreases with increasing
temperature. At 100°C the curves for KS270 and KS1295 are nearly parallel in the almost
whole range of the hardness.
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