Tensile creep of an additively manufactured Ti-48Al-2Cr-2Nb alloy with a layered microstructure

This study investigated the tensile creep behavior of Ti-48Al-2Cr-2Nb alloy with a layered microstructure produced by selective electron beam melting (SEBM). Creep tests were conducted on a range of temperatures from 750 to 850 degrees C, and stresses from 120 to 280 MPa. The stress exponents (n) varied from 6.3 to 5.1 with increasing temperature, and the apparent activation energy (Q(c)) was determined to be 436.8 kJ/mol under 200 MPa. The observations indicated that at 750 degrees C and 800 degrees C, cross-slip bands and deformation twins tend to form in coarse grain (CG) regions. At 850 degrees C, extensive dynamic recrystallization (DRX) concentrated in fine-grained (FG) regions and the heterogeneous interfaces, characterized by discontinuous dynamic recrystallization (DDRX). A small number of continuous dynamic recrystallization (CDRX) grains appeared in CGs and were characterized by sub-grain rotation. The results suggest that local stress concentration induced by deformation twins and cross-slip bands within CGs may nucleate and merge to form cavities.