Study on the reaction mechanism and mechanical properties of aluminum matrix composites fabricated in an Al-ZrO2-B system

The in situ composites with reinforcement volume fraction of 30 vol.% were fabricated by chemical synthesis method in an Al-ZrO2-B system. The reaction mechanism and mechanical properties of the composites were studied. When the B/ZrO2 mole ratio was zero, the reinforcements of the composite consisted of alpha-Al2O3 particles and Al3Zr blocks, whose volume fractions were around 8.74 vol.% and 21.6 vol.%. The ultimate tensile strength, elongation and elastic modulus of the composite at room temperature were 215.2 MPa, 3.0% and 110.6 GPa, respectively. With the increase of B/ZrO2 mole ratios, the ZrB2 particles were formed and the amount of the Al3Zr blocks decreased. When the B/ZrO2 mole ratio reached 2, the Al3Zr blocks almost disappeared and the reinforcements of the composite were composed of alpha-Al2O3 and ZrB2 particles, whose volume fractions were around 14.5 vol.% and 15.5 vol.%. As a result, the ultimate tensile strength and elongation of the composite increased to 245.4 MPa and 12.3%. However, its elastic modulus decreased to 100.4 GPa. The tensile fracture was governed strongly by the amount of Al3Zr in the composites. When the B/ZrO2 mole ratio increased from 0 to 2, the tensile fracture mechanism of the composites transformed from quasi-cleavage to toughness fracture. (C) 2011 Elsevier B.V. All rights reserved.