It is worth mentioning that the yield values reported here are computed as offset yield strength at 0.2 % of plastic strain. In the case of composite with micrometer reinforcing particles of alumina, the ultimate tensile strength is 186.6 MPa, and the yield strength is 83 MPa. These values are exactly two times higher than those of the base metal. For the last composite (with nano-alumina particles), the values of ultimate and yield strength are 134.98 and 57 MPa, respectively (1.41 times higher). The main reason for this enhancement is friction stir processing and the added ceramic particles. This process changes the material's microstructure by refining grain distribution and eliminating the defects and micro-voids through localized plastic deformation. This enhancement is evident for the micro-alumina and without powder composites compared to the other two cases. Furthermore, micro-alumina composite shows an average of 42 % enhancement in strength compared to nano-alumina composite. This can be related to the large ceramic particles that can resist deformation more than nano-size particles.