Mechanical properties and microstructure of Al2O3/TiAl in situ composites doped with Cr

Abstract

Cr-doped Al 2 O 3 /TiAl in situ composites were successfully fabricated by hot-press-assisted exothermic dispersion method with elemental powder mixtures of Ti, Al, TiO 2 and Cr. The effect of the Cr addition on the microstructures and mechanical properties of the Al 2 O 3 /TiAl composites were investigated. The as-synthesized composites consisted of γ-TiAl, α 2 -Ti 3 Al, Al 2 O 3 , and a small amount of Laves phase Ti(Al,Cr) 2 . Microstructure analysis indicates that Al 2 O 3 particles mainly distributed on grain boundaries of the TiAl matrix. As the Cr content increases, the Al 2 O 3 particles are dispersed more fine and homogeneously in the TiAl matrix, which resultes in the increase of the hardness, flexural strength and fracture toughness of the composites gradually. When the Cr content was 3 wt.%, the flexural strength and fracture toughness of the Al 2 O 3 /TiAl composite reaches the top values of 820 MPa and 8.3 MPa·m 1/2 , respectively. The reinforcement mechanism of Cr addition to Al 2 O 3 /TiAl composites was also discussed.