Abstract
Superheat treatment on Al-7Si-0.55Mg melt and its influences on the solidification structure both in the micro-and macroscales, as well as mechanical properties, are studied experimentally. The alloys were first melted and superheated for ∼30 minutes at temperatures between 720 °C and 950 °C. The melts were then cooled slowly to 720 °C before casting into the specimens for microstructural analyses and mechanical property tests. The results show the following. (1) A superheating process above 850 °C for 30 minutes modifies the interdendritic eutectic and is comparable to that achieved by a Sr addition. A high cooling rate is necessary to ensure the modification efficiency. (2) Through superheat treatment, the morphology of Fe-rich phases can range from needlelike to skeleton. This effect is not observed in the case of Sr additions. (3) Superheat treatment reduces slightly the secondary dendrite arm spacing and coarsens the primary grain size. (4) The strength of specimens that underwent a superheat treatment during the melting process can be even 10 MPa higher than those modified by Sr addition.
| Original language | English |
|---|---|
| Pages (from-to) | 799-806 |
| Number of pages | 8 |
| Journal | Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science |
| Volume | 34 |
| Issue number | 13 |
| DOIs | |
| State | Published - 2003 |