Aluminum Foundry Modification Treatment
Targeted addition of sodium or strontium to the melt of aluminum-silicon alloys to suppress the eutectic silicon and form fine streaks. This increases elongation at break.
Physico-Chemical Working Mechanism
The aluminum casting modification treatment involves adding sodium or strontium to the melt. These additions react with the silicon and suppress the eutectic silicon that normally forms in shapeless needles. As a result, the silicon is formed as fine stripes.
Metallurgical Relevance & Risks in Welding
The finer structure of the silicon improves the elongation of the alloy, as it offers fewer anchor points for cracks. However, an excessive addition of sodium or strontium can lead to deformations and weak spots. It is therefore crucial to control the concentration precisely.
Workshop Practice & Instructions
For a successful aluminum casting modification treatment:
1. Determine the exact silicon content of the alloy.
2. Add sodium or strontium in amounts of 0.05 to 0.1 % to the melt (depending on the silicon content).
3. Use a controlled cooling to preserve the finer silicon structure.
4. Monitor the addition amount closely to avoid weak spots.