Fabrication of (TiB/Ti)-TiAl composites with a controlled laminated architecture and enhanced mechanical properties

The (TiB/Ti)-TiAl composites with a laminated structure composing of alternating TiB/Ti composite layers, alpha(2)-Ti3Al interfacial reaction layers of and gamma-TiAl layers were successfully prepared by spark plasma sintering of alternately stacked TiB2/Ti powder layers and TiAl powder layers. And the influence of thickness ratio of TiB2/Ti powder layers to TiAl powder layers on microstructure evolution and mechanical properties of the resulting (TiB/Ti)-TiAl laminated composites were investigated systemically. The results showed that the thickening of alpha(2)-Ti3Al layers which originated from the reaction of Ti and TiAl was significantly hindered by introducing TiB2 particles into starting Ti powders. As the thickness ratio of TiB2/Ti powder layers to TiAl powder layers increased, the bending fracture strength and fracture toughness at room temperature of the final (TiB/Ti)-TiAl laminated composites were remarkably improved, especially for the (TiB/Ti)-TiAl composites prepared by TiB2/Ti powder layers with thickness of 800 mu m and TiAl powder layers with thickness of 400 mu m, whose fracture toughness and bending strength were up to 51.2 MPa.m(1/2) and 1456 MPa, respectively, 293 % and 108 % higher than that of the monolithic TiAl alloys in the present work. This was attributed to the addition of high-performance network TiB/Ti composite layers. Moreover, it was noteworthy that the ultimate tensile strength at 700 degrees C of (TiB/Ti)-TiAl composites fabricated by 400 mu m thick TiB2/Ti powder layers and 400 mu m thick TiAl powder layers was as high as that at 550 degrees C of network TiB/Ti composites. This means the service temperature of (TiB/Ti)-TiAl laminated composites was likely raised by 150 degrees C, meanwhile a good combination of high strength and high toughness at ambient temperature could be maintained. Finally, the fracture mechanism of (TiB/Ti)-TiAl laminated composites was proposed. (C) 2020 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

The (TiB/Ti)-TiAl composites were prepared by spark plasma sintering, and the effect of thickness ratio of TiB2/Ti powder layers to TiAl powder layers on the mechanical properties was investigated. The results showed that the addition of TiB2 particles can significantly improve the bending fracture strength and fracture toughness of the composites, especially at room temperature.