The Effect of Stearic Acid on Microstructure and Properties of (Ti2AlC + Al2O3)p/TiAl Composites

A new type of multiphase nanoparticle-reinforced TiAl matrix composites ((Ti2AlC + Al2O3)(p)/TiAl composites) was successfully prepared by vacuum hot-pressing sintering using Ti powder and Al powder, which were ball-milled with different contents of stearic acid (CH3(CH2)(16)COOH). The component, microstructure, reaction mechanism, and mechanical properties were studied. The results indicated that the composites prepared by adding stearic acid as a process control agent during the ball-milling process not only contained gamma-TiAl and alpha(2)-Ti3Al phases but also Ti2AlC and Al2O3 phases. The results of SEM and TEM showed that the composites were composed of equiaxed TiAl and Ti3Al grains, and the Ti2AlC and Al2O3 particles were mainly distributed along the TiAl grain boundary in chain form, which can effectively reduce the TiAl grain size. Through the room-temperature compression test, the maximum compression stress was significantly improved in those composites that added the stearic acid, due to the reinforcement particles. The maximum compression stress was 1590 MPa with a 24.3% fracture strain. In addition, the generated crack deflection and Ti2AlC and Al2O3 particles could also enhance the toughness of the TiAl alloy. (Ti2AlC + Al2O3)(p)/TiAl composites generated by adding stearic acid played a key role in improving the mechanical properties of the TiAl matrix.