Al–Al3Ti nanocomposites produced in situ by friction stir processing

Aluminum reinforced with a large amount (up to ∼50 vol.%) of nanometer-sized Al3Ti particles can be fabricated from Al–Ti elemental powder mixtures via friction stir processing (FSP). This technique combines the hot working nature of FSP and the exothermic reaction between aluminum and titanium. For the production of intermetallic reinforced in situ composites, FSP can provide (a) severe deformation to promote mixing and refining of the constituent phases in the material, (b) elevated temperature to facilitate the formation of intermetallic phase in situ, and (c) hot consolidation to form a fully dense solid. Due to the fine dispersion of Al3Ti particles, the aluminum matrix has a submicrometer-grained structure. As a result of the high Al3Ti content and very fine microstructure, the composites possess enhanced Young’s modulus and strength.