COST 507 - Repositório Aberto da Universidade do Porto
COST 507 - Repositório Aberto da Universidade do Porto
COST 507 - Repositório Aberto da Universidade do Porto
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GR2<br />
Differential Scanning Calorimetry and Thermodynamic<br />
Calculations aimed at the Development of Al-Mg-Si Cast<br />
Alloys with Cu, Ag and Sm Additions<br />
G. N. Haidemenopoulos and A. N. Vasilakos<br />
Department of Mechanical and Industrial Engineering,<br />
University of Thessaly, Volos, Greece<br />
Abstract<br />
This work has been performed within the framework of <strong>COST</strong> <strong>507</strong> Round II<br />
program on the Al-Mg-Si-Cu system (Leading system 2). DSC measurements<br />
have been performed on three alloys based on the conventional A357<br />
composition with additions of Cu, Ag and Sm. For the three alloys, designated<br />
A357+CU, A357+Cu+Ag, and A357+Cu+Sm, the solidification regimes as well<br />
as the transformation enthalpies for melting and solidification were determined.<br />
The results were compared with predictions of the thermochemical <strong>da</strong>tabase<br />
and software system Thermo-Calc. Additional thermodynamic calculations<br />
included isopleth sections and Scheil solidification diagrams showing the<br />
development of microsegragation. Calculation of the precipitation driving forces<br />
for the strengthening phases Mg 2 Si and AI 2 Cu were conducted as a function of<br />
alloy composition and ageing temperature. These calculations established the<br />
recommended ageing temperatures of the alloys. Application of the modified<br />
ageing treatments (relative to the conventional A357 alloy) resulted in<br />
improved combinations of strength and ductility.<br />
1. Introduction<br />
Aluminum alloy A357, which is based on the Al-Mg-Si system, is widely used in<br />
precision casting applications. The effect of several alloying elements in A357<br />
has been studied e.g. Be additions [89Bru, 83Nag, 84Gra], La additions<br />
[83Bac], as well as Na, Sr and Sb additions [880ze, 86Mai, 89Ape]. It has<br />
been proposed [96Bri] that combined additions of Cu with Ag and Sm could<br />
lead to further enhancement in strength and ductility of precision cast alloy<br />
A357. The present work was conducted in the framework of <strong>COST</strong> <strong>507</strong> Round<br />
II program in order to investigate additions of Cu, Ag and Sm to the<br />
conventional alloy A357. Differential Scanning Calorimetry (DSC) was<br />
employed to determine the melting and solidification regimes as well as the<br />
enthalpies for melting and solidification. The results were then compared with<br />
the predictions of the thermochemical <strong>da</strong>tabase and software program<br />
Thermo-Calc. Further calculations were targeted towards improving the ageing<br />
treatment of the alloys.<br />
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