Abstract Herein we report on the fabrication and mechanical properties of Mg composites fabricated by pressureless melt infiltration of Mg and Mg alloys into porous preforms of TiC and Ti 2 AlC. The latter is a member of the MAX phases – viz. layered, machinable, ternary carbides and nitrides – some of which are relatively light and stiff. In this study, pure Mg and three, commercially available, aluminum-containing Mg alloys – AZ31, AZ61 and AZ91 – were used as matrices at a loading of ≈50 vol%. For the most part, increasing the Al content enhanced the elastic moduli, Vickers hardness values and yield and ultimate compressive strengths. Reducing the particle sizes of the TiC and Ti 2 AlC particulate reinforcements also had a large impact on the mechanical properties. At 1028±5 MPa, the ultimate compressive strength of a TiC–AZ61 composite, in which the TiC particle size distribution is Lorentzian and centered at, d c =0.41±0.01 µm, was ≈40% higher than that of the same composite with coarser TiC particles with a bimodal size distribution centered around d c =1.6±0.1 µm, and 5.8±0.3 µm. In addition, the elastic modulus and Vickers hardness of the former composite were measured to be 174±5 GPa and 3.4±0.3 GPa, respectively. For the Ti 2 AlC reinforced composites, the best properties were obtained when AZ61 was reinforced with Ti 2 AlC particles with d c =0.51±0.01 µm. The enhancements in elastic and mechanical properties are attributed to the presence of a strong interface mediated by the presence of Al in the matrix, finer reinforcement particle sizes and finer grained Mg-matrices. The Ti 2 AlC composites are slightly lighter and can be fabricated at lower temperature than comparable TiC composites; the former are also readily machinable but more expensive.