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

Abstract

A stir-casting process has produced aluminum alloy A356 reinforced with Al2O3 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 Al2O3 was kept constant at 10 vf-%. This research aims to study the effect of Sr on the microstructure and mechanical properties of Al A356/Al2O3 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 Al2O3 particles and stirred again for 3 min to distribute the Al2O3 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 Mg2Si primary in the matrix.