Microstructure and mechanical properties of micro/nano B₄C particle reinforced 6061Al matrix composites

Micro/nano B₄C particle reinforced 6061Al composites with three volume fractions (3vol%, 5vol%, 7vol%) were prepared by advanced powder metallurgy technology (spark plasma sintering +hot extrusion). The microstructure evolution at different stages was observed by SEM, TEM and EBSD. The nano-indentation behavior, tensile properties and friction and wear properties were also tested. Results show that B₄C particles distribute in a network structure after sintering, and the B₄C particles are dispersed uniformly after extrusion. The nano-B₄C particles are distributed in the grains and grain boundaries. The pinning effect of nano-B₄C on the dislocation accumulates a large number of dislocations in the matrix, which provides driving force and overrides the dynamic recovery. Finally, the recrystallization ratio reaches 74%. When the volume fraction of B₄C is 3vol%, the tensile strength, yield strength and elongation of as-extruded B₄C/6061Al composites are 219 MPa, 88 MPa and 22.5%, and a large number of dimples appear in the fracture morphology.