Ti–46Al–4Nb alloy refined and reinforced by in-situ TiC nanoparticles and TiB2 whiskers

Abstract

This paper reports a new type TiAl alloy – refined and reinforced by in-situ TiC nanoparticles and TiB2 whiskers. In this study, high-energy ball milling was performed on AlB2 and graphene to prepare the inoculant. In the process of ball milling, the energy generated will make the agglomerated state of graphene disappear and wrap AlB2 to form the inoculant with core-shell structure. Then, the inoculant was added to the Ti–46Al–4Nb alloy melt. The C, B atoms of the inoculant will act as the active factors to react with the Ti atoms to form in-situ TiC nanoparticles and TiB2 whiskers. TiC nanoparticles can be used as heterogeneous nucleation cores to refine grains and TiB2 whiskers can strengthen the TiAl alloy due to their large aspect ratio and modulus. The results showed that when 0.5 wt% inoculant was added, the room temperature ultimate compressive strength of TiAl alloy will increase from 1542 MPa to 2049 MPa. The high temperature ultimate compressive strength of TiAl alloy will increase from 627 MPa to 988 MPa. In addition, further research has been conducted on the orientation relationship (OR) between the reinforcement and the matrix. By means of transmission electron microscope (TEM) observation and analysis, it was found that TiC, TiB2 had good orientation relationships with TiAl matrix. They had a low degree of mismatch and good combination. At the same time, the Materials Studio software was used to simulate their orientation relationships and the results of simulation were consistent with the experimental results. This further verified that the reinforcements were well combined with the matrix. The TiAl alloy can be refined and reinforced by in-situ TiC nanoparticles and TiB2 whiskers.