COST 507 - Repositório Aberto da Universidade do Porto

Heat Capacity Data on some Al-based Alloys
Fl
C.Y.Zahra and A.-M. Zahra
Centre de Thermodynamique et de Microcalorimétrie, C.N.R.S.
26, rue du 141e R.I.A., F-13331 MARSEILLE CEDEX 3
Abstract
Specific heat capacities were determined on 2 industrial ΑΙ-Si based alloys and on 11
ternary Al-Si-Zn alloys. The data were obtained with the help of a heat flux DSC
apparatus and have a reproducibility of ± 1.5 %. In the case of the industrial alloys, the
Cp-values may be interpolated linearly between 50 and 250 °C. The values for the
ternary alloys lie in general below those derived from the application of the additivity
rule.
1 Introduction
The present study covers Crj-measurements on Al-based alloys made available from
COST 507/Π partners D9 (Dr. G. Neuer) and destined for the databank THERSYST.
Two groups of alloys were studied :
- industrial ones already examined by partners D9. In this way, results of independent
measurements may be compared;
- ternary alloys for which COST partners D3 (Dr. P.J. Spencer) calculated the
thermodynamic properties starting from known data on the binary systems involved.
The ultimate aim is to confront their predictions with experimental data.
2 Experimental
Two technical ΑΙ-Si based alloys prepared by Kolbenschmidt AG were selected for a
comparative study; their chemical compositions (in mass%) and Brinell hardnesses
before the Cp-measurements are given in table 1. The stability of their structural states
was evaluated from DSC runs (fig. 1). Dissolution sets in above 280 °C.
Table 1 : Alloy compositions
KS-4 8.44% Si KS-5 13.46% Si
3.09 % Cu 3.71 % Cu
0.49% Mg 0.87% Mg
0.05% Ni 2.18% Ni
0.60% Fe 0.55% Fe
0.39 % Mn 0.45 % Mn
0.46% Zn 0.08% Zn
0.09 % Ti 0.05 % Ti
0.08 % Pb 0.01 % Pb
0.02 % Sn 0.01 % Sn
HB: 99 HB: 152
The eleven ternary Al-Si-Zn alloys were cast by Vereinigte Aluminiumwerke Bonn.
Their chemical compositions (in atom and mass %) are indicated in table 2 and also
represented in fig. 2. From each alloy including the technical ones, 2 disks 5.9 mm in
diameter and 1 mm thick were machined.
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