Abstract
The microstructure and microhardness evolution of a Ti-15(wt.%)Mo/TiB metal-matrix composite (MMC) during high-pressure torsion (HPT) at 400 °C was studied. The composite was fabricated by spark plasma sintering of a Ti, Mo and TiB2 powders mixture at 1200 °C. In the initial condition, the structure of the composite consisted mainly of body-centered cubic (bcc) Ti solid solution and TiB whiskers. An increase in dislocation density, a considerable decrease in a grain size in the bcc Ti matrix, and breaking/rearrangement of the TiB whiskers were observed during HPT. The (sub)grain size in the bcc Ti matrix attained after 1 revolution was ~75 nm and then gradually decreased to ~55 nm after 5 revolutions. The TiB particle sizes after 5 revolutions was found to be 130–210 nm. The microhardness increased with strain from 575 HV in the initial state to 730 HV after 5 revolutions. Various hardening mechanisms’ contributions in the Ti-15Mo/TiB were evaluated.
Highlights
Titanium and some titanium alloys are used in medicine to a great extent due to good corrosion resistance, high specific strength and excellent biocompatibility
The TiB whiskers in the bcc Ti matrix can be seen in transmission electron microscopy (TEM) images (Figure 1c)
Grain boundaries cannot be distinguished in the bcc Ti matrix; spacing between the TiB whiskers was ~1–1.5 μm
Summary
Titanium and some titanium alloys are used in medicine to a great extent due to good corrosion resistance, high specific strength and excellent biocompatibility. Absolute values of hardness and yield strength of titanium alloys is rather low [2] and limits their use for same specific applications, for example fabrication of scalpels, operating knives or scissors. TiB has a close to titanium density and creates low residual stresses due to a good crystallographic match with the matrix [4,5]. The obtained values of strength and hardness of hexagonal close-packed (hcp) Ti/TiB MMCs were found to be insufficiently high to use this material for production of surgical cutting instruments [7,8]
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