Crystal morphology and growth mechanism of reinforcements synthesized by direct melt reaction in the system Al–Zr–O

In-situ Al3Zr and Al2O3 particulates reinforced aluminum matrix composites were fabricated by the direct melt reaction (DMR) technique in the system Al–Zr–O. Microstructures of the composites and crystal morphology of in-situ formed Al3Zr and Al2O3 particulates were analyzed by scanning-electron microscope (SEM) and transmission electron microscope (TEM). Results indicated that in-situ formed Al3Zr and Al2O3 particles were finer and well distributed in aluminum matrix. Al3Zr particulates with a tetragonal structure are mainly in the shape of polyhedron. A few of them are rectangular. The length/width ratio of the rectangular Al3Zr is less than 2.0 and the maximum size is 4 μm. In addition, submicro Al2O3 particles with a hexagonal structure were also found in this system. Furthermore, it is found that twin may appear in the Al3Zr crystal. The twin plane is (114). The twinning direction is [22̄1].