Hi everyone! I have a question about mechanical properties of the materials. As I understand, when in metals microstructure the grains size decreases, the mechanical properties increases, specially metals strengthening. But I have a discussion with one Prof. who says that this is a minor eefect in Al alloys as compare to the steels. In Al only an Orowan mechanism works. In this mechanism, the dislocation bends between the particles leaving a dislocation ring about each particle. Is he right? Anyone can help me to find the strengthening mechanism in metals. Thanks a lot.