Microstructures and the improved mechanical properties of AZ91 alloy by incorporating Ti-6Al-4V particles

Magnesium (Mg) based composites are often difficult to achieve the trade-off between strength and ductility. The titanium (Ti) metal particles, which show better wettability and ductility than ceramic particles, are selected as reinforcements to simultaneously enhance the strength and plasticity of Mg alloys. In this work, the TC4 (Ti-6Al-4V) particles (2, 4 and 6 vol. %) reinforced AZ91 composites were successfully fabricated by the mechanical and ultrasound-assisted stirring method. By incorporating 4 vol.% TC4 particles, the composite reached the optimum yield stress, ultimate tensile stress, and elongation of 257 MPa, 370 MPa and 18.7%, respectively. The microstructural characterizations revealed that the fine and coarse grains were observed in the AZ91 and TC4/AZ91 composites. The dynamic recrystallization behavior was retarded in the TC4/AZ91 composites, which was rooted in the TC4 particles and fine Mg17Al12 phase. Transmission electron microscopy (TEM) showed that the interfacial product at TC4/Mg interface was Al3Ti phase. Based on the quantitative calculations, the strengthening effects of the 4TC4/AZ91 composite were mainly the coefficient of thermal expansion strengthening, grain refinement strengthening and the deformable TC4 particles.