Improved structural homogeneity and mechanical properties of nanoparticles reinforced Al composites after orthogonal thermomechanical processes

Orthogonal thermomechanical processes consisting of a hot extrusion and the subsequent orthogonal rolling are proposed to disperse the nanoparticle clusters and optimize the grain structures of matrices in in-situ synthesized TiB₂ particles reinforced Al-Zn-Mg-Cu composites. The particle distributions and grain structures of composites are investigated by scanning electron microscopy, electron backscatter diffraction and neutron diffraction techniques. Compared with the hot extruded counterparts, the composites fabricated by the new process exhibit uniform particle distributions, less elongated grains and weak textures, owing to the strain path change and enhanced recrystallizations. Both high strength (669 MPa and 606 MPa) and good ductility (11.1% and 14.2%), are achieved in the resultant composites along the longitudinal and transverse direction respectively. The underlying mechanisms for modified mechanical properties are discussed in detail from the perspectives of the uniform TiB₂ particles and homogenized grain structures.