Formation of TiC/Ti2AlC and α2+γ in in-situ TiAl composites with different solidification paths

Abstract

In order to improve the mechanical properties of TiAl alloys, TiAl composites with different solidification paths were synthesized by metallurgical method. Results show the TiC disappears and Ti2AlC increases when the Al content is more than 42% (at.%, similarly hereinafter). Small TiC particles are located in Ti2AlC grains with irregular shapes when the Al content is 40%, and they translate into clubbed Ti2AlC with increasing of Al. This metallurgy method can solve the defects of the Al lacking and the residual TiC. The γ phase increases between lamellar colonies with the increasing of Al. When the Al content is 48%, the fully lamellar structure transforms into a duplex microstructure and there are small Ti2AlC phases in γ phases, because the forming of Ti2AlC phase must consume Al. The compressive strength increases up to 1678.68 MPa as Al content is 46 at.%, and then decrease to 1460.22 MPa, the compressive strain increases and then keeps stabilization with the increasing Al. The maximum strength improves 38.82% and the maximum strain improves 121.37%. The Ti2AlC/TiAl composites fracture behaviors are load transferring behavior, crack deflection, trans-lamellar cracking and extraction of carbide reinforcements. The Ti2AlC phase and the fully lamellar structure improve the mechanical properties.