Insights into in-situ TiB/dual-phase Ti alloy interface and its high load-bearing capacity

To better understand the strengthening mechanism of in-situ formed TiB reinforcements in dual-phase Ti6Al4V alloy, the interface characters and properties of alpha-Ti/beta-Ti/TiB system were thoroughly investigated with the combined use of high-resolution transmission electron microscopy (HRTEM), abinitio calculations, and indentation tests. The ab-initio calculations suggest that the highly coherent (100)(TiB)/((1) over bar 21)(beta-Ti), phase boundary (PB) has fairly low interface energy of 0.082 J/m(2) with an exceptionally high adhesion strength of 6.04 J/m(2), owing to the formation of strong interfacial Ti-B ionic bonds. The semi-coherent (20 (1) over bar)(TiB)(0001)(alpha-Ti) interface shows a relatively higher interface energy of 1.442 J/m(2) but still with a fairly high adhesion strength of 4.95 J/m(2). With the obtained interfacial energetics, thermody-namics analyses were further carried out to explore the nucleation mechanism of alpha-Ti in TiB reinforced Ti6Al4V composite. Superior to the heterogeneous nucleation at TiB/beta-Ti interface, the homogeneous nucleation of alpha-Ti within the beta-Ti phase can be more energy-preferred, due to its lower nucleation energy barrier and critical radius. Further indentation tests under various loads of different modes confirmed a remarkably enhanced load-bearing capacity of dual-phase Ti6Al4V alloys, under the critical significance of the strong interfacial bonding achieved by reinforcements of in-situ formed TiB. (C) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.