Strontium-based additive for enhanced aluminum A356-reinforced Al₂O₃ composite mechanical properties and microstructures

A stir-casting process has produced aluminum alloy A356 reinforced with Al 2 O 3 metal matrix composites (MMCs). The strontium was added into molten Al A356 to improve the mechanical properties of composites. The strontium used varied from 0.046 wt.% to 0.070 wt.%, while Al 2 O 3 was kept constant at 10 vf-%. This research aims to study the effect of Sr on the microstructure and mechanical properties of Al A356/Al 2 O 3 composite. The A356 was melted at 800 °C and mixed with Al-5TiB, Al-5Sr, and Mg as a master alloy of the matrix, then flushed with argon to remove all the gas bubbles from liquid aluminum and stirred for 2 min afterward, it was poured with Al 2 O 3 particles and stirred again for 3 min to distribute the Al 2 O 3 particles in molten Al matrix. The composites produced then characterized both microstructural analysis and mechanical properties. The maximum strength, elongation, and hardness of composites were achieved at 0,046 wt.% Sr with the value of 185 MPa, 4.00%, and 45.3 HRB, while strength, elongation, and hardness of unreinforced were 101 MPa, 2,72%, and 40 HRB respectively and further addition of Sr mechanical properties decreased. The increase in the strength is due to the refinement of Mg 2 Si primary in the matrix.