Microstructure and Mechanical Properties of Hybrid AZ91 Magnesium Matrix Composite with Ti and SiC Particles

In this paper, a new hybrid metal matrix composite, named AZ91/(SiC + Ti)_p, is presented. The commercial AZ91 magnesium alloy was chosen as the matrix. The composite was reinforced with both SiC and Ti particles. The investigated material was successfully fabricated using stir casting methods. Microstructure analyses were carried out by digital and scanning electron microscopy with an energy-dispersive X-ray spectrometer (SEM + EDX). Detailed investigations disclosed the presence (besides the reinforced particles) of primary dendrites of the α phase, α + γ eutectic and some part of discontinuous precipitates of the γ phase in the composite microstructure. The composite was characterised by uniform distribution of the Ti particles, whereas the SiC particles were revealed inside the primary dendrites of the α phase, on the Ti particles and in the interdendritic regions as a mixture with the α + γ eutectic. Both the tensile and compression strength as well as the yield strength of the composite were examined in both uniaxial tensile and compression tests at room temperature. The fabricated AZ91/(SiC + Ti)_p hybrid composite exhibited higher mechanical properties of all those investigated in comparison with the unreinforced AZ91 matrix alloy (cast in the same conditions). Additionally, analyses of the fracture surfaces of the AZ91/(SiC + Ti)_p hybrid composite carried out using scanning electron microscopy (SEM + EDX) were presented.