Strong compressive γ-TiAl alloy produced by dual-wire-fed electron beam directed energy deposition: Microstructural evolution and strengthening mechanisms

Abstract

Dual-wire-fed electron beam directed energy deposition (EB-DED) of TiAl alloy is of increasing interest due to its potential to produce high performance components at low cost. However, the strengthening mechanisms involved, in particular the complex relationship between microstructure and mechanical properties, are still unclear. This study uses a combination of experimental fabrication and numerical simulation. The aim is to investigate the microstructural evolution and strengthening mechanisms of a fully columnar γ-TiAl alloy produced by the dual-wire-fed EB-DED technique. The results show that cyclic heating significantly increases the dislocation density in the TiAl alloy. In addition, dislocation networks, twinning intersections and dislocation-twin interactions were observed. Compression test results show that the dual-wire-fed EB-DED prepared γ-TiAl alloy exhibits 26% higher yield strength and fracture toughness, as well as 25% higher work-hardening stress compared to the traditionally processed TiAl alloy of the same composition. The nanoscale twinning and interaction structures are identified as the unique strengthening mechanisms, contributing 194 MPa to yield strength and 1196 MPa to work hardening. This study provides valuable insights into the microstructural characteristics and strengthening mechanisms of TiAl alloy produced using the dual-wire-fed EB-DED.