Microstructural evolution and mechanical properties of Ti43Al alloy by directional annealing

The directional annealing technique is widely used to prepare columnar grains or single crystals. To investigate the effect of hot zone temperature and temperature gradient on the growth of columnar crystals, Ti43Al alloys were heat treated by the directional annealing technique and their mechanical properties were tested. The results show that columnar grains with a maximum size of 22.29 mm can be obtained at a hot zone temperature of 1,350 °C and a temperature gradient of 8 K·mm⁻¹. During the directional annealing process, Ti43Al alloys are heated to α single-phase domain to start the phase transformation. Columnar grains with a microstructure of fully lamellar colonies are obtained at different hot zone temperatures and temperature gradients. The distribution of the orientation difference for the α₂ phase was found to be more random, suggesting that the growth of the columnar crystals may be stochastic in nature. Tensile testing results show that the strength and elongation of directional annealed Ti43Al alloy at 1,400 °C-8 K·mm⁻¹ are 411.23 MPa and 2.29%, and the remaining directional annealed alloys show almost plasticity.