Mechanical, tribological and electrochemical corrosion properties of in-situ synthesized Al2O3/TiAl composites

摘要

TiAl-based composites reinforced with different weight fractions of Al2O3 have been successfully synthesized by hot-pressing using the pre-alloyed Ti-45Al-7Nb-0.2B and Nb2O5 powders. The microstructures, mechanical and tribological properties of composites were examined. The as-sintered TiAl composites mainly consist of gamma-TiAl phase, alpha(2)-Ti3Al phase, gamma/alpha(2) lamellar colony, TiB2 particles and Al2O3 particles. The microstructure can be refined by synthesizing Al2O3 particles. The volume fractions of alpha(2) phase and alpha(2)/gamma lamellar colonies increased with the increasing of Al2O3 content. When the Al2O3 content increases to 0.5 wt %, the composite exhibited the best comprehensive mechanical properties with the yield stress of 1032 +/- 13 MPa and fracture strength of 2668 +/- 15 MPa. For the Al2O3/TiAl composites, the fracture type is mainly composed of transgranular, translamellar and delamination fracture. The friction coefficient of 0.5 wt % Al2O3/TiAl composite is lower than other TiAl composites due to its homogeneous distribution of Al2O3 particles. The main wear mechanism of Al2O3/TiAl composites was determined to be abrasive wear along with plowing grooves. Addition of Al2O3 particles can improve the corrosion resistance of TiAl composites.