Friction stir extrusion and mechanical alloying of LM13 casting ingot to produce LM28 tubes

Abstract

Friction Stir Extrusion (FSE) is applied on the as-cast LM13 aluminum alloy to produce tubes accompanied with the microstructural modification. Then, the process was employed to transform LM13 to LM28 alloy by mechanical alloying by adding Si particles during the process. In addition, a numerical model on the Deform 3D software is developed to simulate the process and investigate the temperature and strain distributions at different zones as well as the material flow over the process. The experimental and numerical results show that the peak temperature and strain of 460 °C and 200 are attained in the zone 6–10 mm after the conical part finish, where the material completely enters the tube channel. The temperature and strain distributions were varying through the tube wall, and the result is that the average Si precipitates’ size in the wall inside reduced to almost 0.8 μm while is 2 μm at the center of the tube wall. Furthermore, the material flow from the primary cylindrical ingot towards the tube wall was not uniform in the sample cross-section due to tool design, and the velocity of material movement at various zones was different. Mechanical alloying of LM13 alloy, by the addition of Si particles in ∼6 %, transformed the alloy to LM28 by increasing the silicon content from 12.2 to 19.2 %. The ultimate compression strength of the LM13 base metal increased from 84.7 to 138.7 MPa and 158.2 MPa, respectively, for LM13 and LM28 by breakage of needle-like Si precipitates and fine dispersion of them in the aluminum substrate.