In Reply to: Internal shrinkage in Al castings. posted by kadam S. B. on 05/19/02 at 5:46 AM:
For the alloy LM 6, composition and structure are very important to avoid internal shrinkage. If the alloy ist near the eutectic composition (12,6 - 13,4 % Si), it is necessary to have a "not - lamellar" Silicon. This is done with a addition of 10 - 20 ppm Phosphorus.
If the Silicon is 11,0 - 11,7 %, then a smaller addition of phosphorus is recommended (5 - 10 ppm) and a good grain refining is important (AlTiB). Ask your ingot - supplier to produce ingots with the correct structure !!
with best regards