Investigation on heat treatment strategy eliminating heterogeneity and anisotropy of TiAl alloy fabricated using twin-wire directed energy deposition-arc

Additively manufactured TiAl alloy presents heterogeneous and anisotropic microstructure and mechanical properties, resulting from the characteristic of layer by layer deposition, which is detrimental to its further application. In this work, TiAl alloy is built using an innovative twin-wire directed energy deposition-arc (TW-DED-arc). In order to eliminate the heterogeneity and anisotropy of additively manufactured TiAl alloy, the effect of heat treatment on the TiAl alloy fabricated by TW-DED-arc process is investigated. The experimental results indicate that the suitable heat treatment process (1420 °C, 2 min, furnace cooling) can effectively eliminate the heterogeneity and anisotropy of TiAl alloy fabricated using TW-DED-arc process. After the heat treatment, the layer-band like microstructure transforms into homogeneous fully lamellar colony with relatively smaller size, microstructure homogeneity is significantly improved, and the microstructure is also closer to equilibrium state. Also, the microhardness distribution of sample becomes more homogeneous, whose anisotropy is also effectively weakened. •The TiAl alloy is fabricated successfully by twin-wire directed energy deposition-arc•The additively manufactured TiAl alloy presents heterogeneous and anisotropic microstructure and mechanical properties•The heat treatment method to eliminate the heterogeneity and anisotropy of additively manufactured TiAl alloy is obtained successfully•The layer-band like microstructure transforms into homogeneous fully lamellar colony after the heat treatment•The heterogeneity and anisotropy of mechanical properties are significantly improved after the heat treatment.