Abstract: The influence of the mass fraction of B₄C on the microstructures and tribological properties of the B₄C-reinforced,Cu-based composite,a vehicle clutch material fabricated by spark plasma sintering(SPS),was investigated with X-ray diffraction,scanning electron microscopy and conventional mechanical probes.The preliminary results show that the B₄C mass-fraction had a major impact.To be specific,as the B₄C-content increased from 10% to 50%(wt),the composite density increased,the wear-resistance,average and peak friction-coefficients changed in an increase-decrease manner,accompanied by a decrease of the friction stability coefficient,possibly because of the increases of B₄C agglomeration and because of the B₄C clusters peeling off.At a B₄C mass fraction of 50%,agglomeration of B₄C particles became fairly obvious.Much work remains to be done to optimize the B₄C mass fraction and to fully understand the phase-structures of the B₄C-reinforced Cu-based composite material.