Hardness–depth profile of a carbon-implanted Ti–6Al–4V alloy and its relation to composition and microstructure

Abstract

The variation of mechanical properties (hardness, indentation modulus) within a carbon-implanted region of a Ti-6Al-4V alloy-about 350-nm thick-was, for the first time, related with the microstructure and the chemical composition with a depth accuracy as small as ±20 nm. Microstructure, chemical composition, and mechanical properties of the implanted alloy were determined using transmission electron microscopy, Auger electron spectroscopy, and nanoindentation, respectively. The microstructure within the implanted region contains TiC precipitates, the density of which changes with depth in accordance with the carbon content. The hardness depends on the precipitate density: the maximum hardness occurs at the depth where an almost continuous TiC layer had formed. The depth profiles of hardness and indentation modulus were measured using three different methods: the cross-section method (CSM); the constant-load method (CLM); and the load-variation method (LVM). Only the hardness-depth profile obtained using the CSM, in which the indentations are performed perpendicular to the hardness gradient on a cross section of the specimen, reflects the microstructural variations present in the implanted region.

Ion implantation of titanium based biomaterials

“…In zones with a smaller TiC precipitate density, the hardness can be quantitatively explained as due to TiC dispersion hardening. The possibility to truly trace the hardness-depth profile of an ion implanted region and to relate this hardness-depth profile with the local variations in microstructure and composition augurs for the development of property-tailored ion implantation procedures [113]. Just to highlight the levels of hardness attainable, a threefold increase in microhardness at loads of 1-2 g is reported in titanium alloys [114][115][116].…”