Friction welding is widely used as a mass-production method in various industries. Joining of ceramic-metal is one of the most essential needs of many industrial applications. Experiments were performed to observe the deformation characteristics of 6061 aluminum alloy after joining with alumina using friction-welding process at different rotational speeds and to relate difference in grain size with differences in deformation behavior. In the present study, electron microscopy and X-ray diffraction profile analysis were used to study the effect of plastic deformation of interface material on the grain size of 6061 aluminum alloy when there is a joint with the ceramic. The effect of rotation speed and the degree of deformation appeared to be high on the 6061 Al alloy than on the ceramic part. Results showed different deformation mechanisms at different rotational speeds and confirmed unambiguously the change in crystalline grains as a result of deformation mechanisms.