Development of a Wear Resistant Aluminum Alloy for Automotive Components 1999-01-0350
Hypereutectic Al-Si alloy 390, containing large amounts of hard silicon particles, has mainly been used for wear-resistant alloy applications. In the case of hypereutectic Al-Si alloys, the primary silicon particle size and distribution must be controlled to obtain stable wear resistance. The service life of furnaces and molds is shortened by the high melting and casting temperatures required for controlling primary silicon. Furthermore, machinability is degraded by large primary silicon particles. To overcome these problems, a new wear-resistant Al-Si alloy has been developed which provides good castability and machinability. This alloy also has wear resistance and mechanical properties similar to those of the 390 alloy. Specifically, the problems regarding castability and machinability were solved by decreasing the silicon content of the 390 alloy, but that also reduced wear resistance. However, good wear resistance was achieved for the new alloy through uniform dispersion of the fine intermetallic compounds. The chemical elements other than silicon, especially Fe, Mn and Cr, are well suited to that purpose. Furthermore, several techniques have been developed to control primary silicon particle size and distribution as a result of investigating their relationship with the melting and solidifying conditions. At the same time, it was found that the addition of minor elements such as Ti, B and Be is effective in suppressing shrinkage cavities.