Study of the Influence of TiB Content and Temperature in the Properties of In Situ Titanium Matrix Composites

Abstract

This work focuses on the study of the microstructure, hardening, and stiffening effect caused by the secondary phases formed in titanium matrices. These secondary phases originated from reactions between the matrix and boron particles added in the starting mixtures of the composites. Not only was the composite composition studied as an influencing factor in the behaviour of the composites, but also different operational temperatures. Three volume percentages of boron content were tested (0.9 vol %, 2.5 vol %, and 5 vol % of amorphous boron). The manufacturing process used to produce the composites was inductive hot pressing, which operational temperatures were between 1000 and 1300 • C. Specimens showed optimal densification. Moreover, microstructural studies revealed the formation of TiB in various shapes and proportions. Mechanical testing confirmed that the secondary phases had a positive influence on properties of the composites. In general, adding boron particles increased the hardness and stiffness of the composites; however rising temperatures resulted in greater increases in stiffness than in hardness.

Microstructure and Mechanical Properties of Ti-TiH2 Based Matrix Composites Reinforced with xTiB2 Particles Processed by Powder Metallurgy

“…For the U-c sample, only Ti concentration can be achieved with a lamellar-shaped microstructure, confirming the dehydrogenation process and the presence of the primary α-Ti phase as described in the XRD section. Moreover, it is observed that by increasing the amount of B, the size of precipitates also increased; as reported by C. Arévalo et al [35]. Thus, reinforced samples showed a major concentration of Ti as the main constituent of the matrix with the presence of B-enriched zones (remaining and large TiB 2 particles).…”

“…The microhardness for the R10 and R30 samples increased until reaching relatively constant values around 500 HV. Microhardness values obtained in this investigation were 122 and 112% higher than those achieved for a Ti matrix reinforced with 2.5 and 5 vol.% of amorphous Boron sintered by inducive Hot Presing (iHP) process at 1100 and 1300 • C [35]. On the other hand, microhardness values obtained by the SPS process at 900 • C, with the usage of TiB 2 reinforcement particles (10 vol.%) and hydride-dehydride powders (balance) [34], can be compared with those obtained between 850 and 1100 • C in the present work; the microhardness values obtained in this work are higher than those reported by Izui H et al (400 HV) [34] improving hardness values around 20% for the R10 sample obtained here (481 HV approximately, interpolating between 850 and 1100 • C).…”

“…The "a" lattice parameter for the set of the experimental conditions has a lower deformation in comparison with the Ti AR "a" parameter (under 2.9768 Å), with a small drop of the R10 and R30 samples at 1100 • C (around 2.960 Å, for the U and R samples as well). Those results can be expected since it is well established that incorporating B in substitutional positions in the HCP structure of Ti shrinks the unit cell [35,36], even demonstrating that the saturated α-Ti-TiH 2 solid solution losses H due to the dehydrogenated reaction and the formation of the TiB phase due to the reaction in the Equation (1) during the PM sintering process. The lattice parameters of the α-Ti solid solution after the PM process are greater than those of pure Ti (a = 2.951 and c = 4.684 Å) [37].…”

Effect of TiB Orientation on Near-Threshold Fatigue Crack Propagation in TiB-Reinforced Ti-3Al-2.5V Matrix Composites Treated with Heat Extrusion

“…Prior work has demonstrated that the mechanical properties of stainless steels [15] and of alloys of magnesium [16], cobalt–chromium–molybdenum [17], and titanium [18,19,20,21,22,23,24,25,26,27,28,29,30] can all be improved via the addition of boron. The combination of titanium and boron generates whiskers of titanium boride (TiB) as a result of the reaction Ti + TiB 2 → 2 TiB.…”