Effect of carbon content on interfacial microstructure and mechanical properties of a vacuum hot-compressed bonding titanium-steel composite

Abstract

Vacuum hot-rolled bonding (VHRB) titanium (Ti)-steel clad composites have been increasingly serving in both severe corrosion and heavy load conditions, and their overall properties severely depend on the microstructure of interfacial reaction layer. Notably, introducing an appropriate interdiffusion barrier to minimize the brittle Fe–Ti intermetallics has still been a popular scheme for optimizing their interfacial properties. In this work, with two low-alloyed steels of 0.06 and 0.16 wt% carbon (C) contents employed, the pure Ti -steel composite samples were successfully prepared via vacuum hot-compressed bonding (VHCB) in Gleeble-3500 system under the identical temperature/reduction/rate condition of 850 °C/70 %/0.01s−1. The interfacial reaction, microstructure and tensile property in two Ti-steel composites were investigated to estimate the C content effect via various characterizations, and the mechanisms were clarified. Results indicated that the diffusion of Ti, Fe and C mainly occurred in the interfacial reaction layers of two composites, and accordingly the reaction products of TiFe, TiFe2 and TiC formed, together with the C-depleted α-Fe zone. The nanoscale TiC particles were mainly located at the steel side, and increased with the increasing C content. Correspondingly, the brittle TiFe layer and TiFe2 layer decreased due to the increased TiC layer acting as a diffusion barrier. This led to an evident decrease of percent cleavage fracture area (CA, %) from 77% to 52% and a significant increase of interfacial tensile strength from 182 to 344 MPa.