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To provide a new idea to reduce anisotropy for sheets in the thickness direction by microstructure modification and, meanwhile, maintain or even enhance tensile performance, the in-situ ZrB2particle/AA7085 composite sheets with thicknesses of 1, 2, 3, and 6 mm were investigated. The as-cast grain size was significantly refined by the heterogeneous nucleus of the ZrB2particle. The microstructure results show that severe hot deformation converts as-cast disordered microstructure into a sequential microstructure by crushing the remanent phases and matrix into a fiber structure. After the solid solution and aging heat treatment, the composite sheets exhibit largely recrystallized grains compared with partially recrystallized grains in the matrix sheets, and weak or even free texture exists in the composite. The grain size in the composite sheets decreases with the increase in thickness reductions. For the thickness range of 1–3 mm, the composite sheets maintain a similar tensile performance as that in matrix sheets, while the strength and ductility in the 6-mm-thick composite sheet are improved.

In-situ ZrB2/AZ91 magnesium matrix composite was successfully synthesized with Al/K2ZrF6+NH4BF4 by Direct Melt Reaction (DMR). The microstructures of the ZrB2/AZ91 magnesium matrix composite fabricated by direct melt mixing method were investigated. The results show that the size of ZrB2 particles is less than 1μm and even reaches to 100nm and the shape, amount and size of the β-Mg17Al12 phase in magnesium matrix composite have been greatly changed due to ZrB2 heterogeneous nuclei.