Abstract
TiB2 particle reinforced 7075Al based composite was fabricated by powder metallurgy and hot extrusion, and the microstructure evolution and precipitation behavior during solution and artificial aging were examined. It was found that the addition of TiB2 particles promoted the dynamic recrystallization during hot extrusion and the static recrystallization during solution, which effectively refined the grain structure. TiB2 particles did not change the precipitation sequence of solid solution → Guinier Preston zones → metastable η' phase → stable η phase, while they strongly retarded the precipitation kinetics. The reaction took place at the interface between TiB2 particles and Al matrix, leading to the formation of a uniform and continuous Mg-bearing layer surrounding TiB2 particles. Both TiB2 particles and precipitations contributed to enhancing the mechanical properties. TiB2/7075Al composite reached the peak hardness of 170.9 HV and strength of 594 MPa after 36 h aging, while 7075Al reached the peak hardness of 169.6 HV and strength of 561 MPa after 24 h aging. TiB2/7075Al composite always exhibited lower friction coefficient and higher wear resistance than 7075Al in any aging state. Moreover, the wear resistance was always the lowest in under-aging state for both TiB2/7075Al and 7075Al, while it is highest in peak aging-state.
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