Hardness of the TiB2/7075 composite increased with increasing deformation t
emperature. In the annealed TiB2/7075 composite, a great amount of fiber-li
ke MgZn2 phases (about 1 mum in length) and small MgZn2 phases (about 100 n
m in size) were precipitated nearby the grain boundaries where the TiB2 par
ticles exist. After deformation at 300 degreesC, some of the large precipit
ates and all the small precipitates in these area dissolved into the matrix
, meanwhile, fine precipitates were formed in grains. After deformation at
450 degreesC, all the precipitates in the annealed composite dissolved into
the matrix, and new phases were precipitated in grains. The dissolution of
the large fiber-like precipitate makes the saturation level of the matrix
increased and leads to an increased solution hardening and natural aging, w
hich contribute much to the hardening effect.