Effect of beam current on microstructure, phase, grain characteristic and mechanical properties of Ti-47Al-2Cr-2Nb alloy fabricated by selective electron beam melting

Selective electron beam melting (SEBM) is a promising manufacturing technology, which offers several processing parameters to select to change microstructure and even to tailor the microstructure. In this paper, the influence of beam current on microstructure, phase composition, grain boundary misorientation and mechanical performances of a Ti-47Al-2Cr-2Nb alloy produced by SEBM was investigated. The results illustrated that with enhancing the beam current, the microstructure changed from fine duplex with the average grain size of 3.02 μm to near gamma structure with the average grain size of 6.28 μm. The volume fraction of B2 phase gradually increased from 2.8% to 18.8% with increasing beam current from 4.5 mA to 8.5 mA. The high angle grain boundary (89 ± 3°) gradually increased and the low angle grain boundary (1-5°) continuously decreased with the enhancing beam current. The ultimate compression strength (UCS) of SEBM-processed TiAl alloy decreased from 2930.95 MPa to 2456.82 MPa and the strain (δ) decreased from 34.82% to 27.44% with increasing the beam current from 4.5 mA to 8.5 mA. Recovery and recrystallization could be observed within the as-built samples, and the effect of beam current on these processes was investigated.