Study on the reaction mechanism and mechanical properties of aluminum matrix composites fabricated in an Al–ZrO 2–B system

Abstract

The in situ composites with reinforcement volume fraction of 30 vol.% were fabricated by chemical synthesis method in an Al–ZrO 2–B system. The reaction mechanism and mechanical properties of the composites were studied. When the B/ZrO 2 mole ratio was zero, the reinforcements of the composite consisted of α-Al 2O 3 particles and Al 3Zr 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/ZrO 2 mole ratios, the ZrB 2 particles were formed and the amount of the Al 3Zr blocks decreased. When the B/ZrO 2 mole ratio reached 2, the Al 3Zr blocks almost disappeared and the reinforcements of the composite were composed of α-Al 2O 3 and ZrB 2 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 Al 3Zr in the composites. When the B/ZrO 2 mole ratio increased from 0 to 2, the tensile fracture mechanism of the composites transformed from quasi-cleavage to toughness fracture.