Interface characteristics of Ti6Al4V-TiAl metal-intermetallic laminate (MIL) composites prepared by a novel hot-pack rolling

Ti6Al4V (wt%)/Ti-44Al-8Nb-0.2W-0.2B-0.03Y (at.%) (high Nb-TiAl) metal-intermetallic laminate (MIL) composite with a defect-free interface was successfully prepared by hot-pack rolling and the interface microstructure was characterized by XRD, SEM, EBSD, and TEM techniques. The results showed that the interface was about 260 μm thick and consisted of four different microstructure regions. The thickness of each region was about 60-80 μm and the microstructure of the four regions consisted of acicular O, α2, and β/B2 phases; acicular α2 phase; acicular α2 and β/B2 phases; and acicular γ, α2, and β/B2 phases respectively. The resulting microstructure of the interface region was attributed to the interdiffusion of Ti atoms from the starting Ti6Al4V alloy layer to the high Nb-TiAl alloy layer and Al and Nb atoms from the high Nb-TiAl alloy layer to the Ti6Al4V alloy layer. The formation of acicular α2 and γ phases was diffusion-controlled and the Nb segregation at the interface caused the formation of O phase which had specific relationships with α2 and β/B2 phases. The detailed interface microstructural evolution of the Ti6Al4V/high Nb-TiAl MIL composite and the Vickers hardness of the composite are also discussed in this paper.