TiAl3 nucleation mechanism and atomic-scale interface features in the Al/Ti composite structures

Abstract

In this work, Al/Ti composite structures are obtained by isothermal compression at 550 °C and then annealed at 500–650 °C, respectively. The element diffusion behavior , TiAl 3 nucleation mechanism and atomic-scale structure at the Al/Ti interface are systematically investigated by different material characterization methods. It is found that with the increasing annealing temperature, the average grain size of TiAl 3 increases from 0.47 to 2.27 μm and the diffusion rates of Al and Ti significantly accelerate, accompanied by the change of interlayer thickness from 0.4 to 74.6 μm. The diffusion of Al and Ti along the grain boundary of TiAl 3 is observed directly, but Al is dominant diffusion element. The nucleation density of TiAl 3 at the Ti/TiAl 3 interface is higher than that at Al/TiAl 3 interface. Moreover, the growth of the TiAl 3 layer is hindered by the enrichment of Si, V, and Mg. The atomic arrangement at the three-dimensional Ti/TiAl 3 interface is disturbed by the aggregation of Si, Al, and V, thus forming the short-range ordered Ti–Al(Si, V) structures with serious lattice mismatch . With an increase in the annealing temperature, the incoherent Al/TiAl 3 interface with obvious misfit dislocations transforms into the semi-coherent one with low lattice mismatch.