Effects of Titanium and Boron Additions with Mechanical Stirring on Mechanical Properties in Al-Si Alloys

Abstract

Al-Si based alloys are widely used to automobile parts for weight reduction. The mechanical stirring method was performed to achieve the homogeneously dispersed strengthening phases such as AlB₂, Al₃Ti and TiB₂ phases since the specific gravity of strengthening phases is different from the Al matrix. 500 rpm of mechanical stirring results in well dispersion of strengthening phases compared with lower speed (100 rpm) and higher speed (1,000) stirring rate. The higher elastic modulus, hardness and good wear resistance is obtained in the Al-12 mass%Si-2.3 mass%Ti-1 mass%B alloy due to the formation of strengthening phases such as Al₃Ti and boride containing (AlTi)B₂ compared with Al-12 mass%Si, Al-12 mass%Si-2.3 mass%Ti and Al-12 mass%Si-1 mass%B alloy. Relationship between the microstructure and mechanical properties is discussed based on the solidification phenomena.