Porous Ti-Nb alloys are promising candidates for biomedical applications. In the present study, alloy powders containing 60 wt-% Nb were prepared by high-energy milling of Nb, Ti, and/or TiH2 powders. The high-energy milling process was carried out in a planetary ball mill. The starting and as-milled materials were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM). Elemental (Nb, and Ti) and TiH2 powder mixtures with composition Nb-40wt%Ti were mechanically alloyed for 2 to 30 h. The formation of a BCC Nb(Ti) solid solution by high-energy milling using elemental Ti powder to produce Nb-40Ti was observed after milling for 30 h. A HCP-Ti solid solution was formed after milling for 30 h due to the partial decomposition of titanium hydride powder mixture during high-energy milling.

The present work reports on the preparation of two-phase TiSS+Ti6Si2B alloys by high-energy milling and subsequent heat treatment. The milled and heat-treated products were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and microanalysis via WDS. Results indicated the dissolution of silicon and boron atoms into the Ti lattice to form supersaturated solid solutions during the ball milling of Ti–10Si–5B and Ti–20Si–10B powders. TiB2 precipitates were formed during ball milling, and the metastable structures were decomposed due to the released heat from its exothermic formation. After heat treatment at 1100°C for 4h, the equilibrium microstructures of the Ti–10Si–5B and Ti–20Si–10B alloys indicated the majority presence of the Ti and Ti6Si2B phases. TiB precipitates were found in Ti–10Si–5B and Ti–20Si–10B powders after heat treatment at 1200°C for 16h, indicating that the composition was moved from two-phase Ti+Ti6Si2B region to the three-phase Ti+Ti6Si2B+TiB field.

Recently, it was identified the existence of a new intermetallic phase in the Ti-Si-B ternary system with atomic composition near Ti6Si2B. In the present work, we report on the phase transformations during the preparation of Ti-22.2Si-11.1B and (TiH2)-22.2Si-11.1B (at.-%) powders in a planetary Fritsch P-5 ball mill from high-purity elemental powders. To understand the phase transformations, powder Ti-22.2Si-11.1B and (TiH2)-22.2Si-11.1B samples milled for 90 h were vacuum heated at various temperatures. The starting materials and milled powders were characterized by means of X-ray diffraction (XRD), scanning (SEM) and transmission (TEM) electron microscopes, and differential scanning calorimetry (DSC). Results indicate that the Ti peaks widen and weaken with the increasing milling time and the silicon was practically dissolved into Ti and TiH2 lattices during milling and formed solid solutions in pre-alloyed Ti-22.2Si-11.1B and (TiH2)-22.2Si-11.1B powders, respectively. The use of titanium hydride instead of titanium as starting material allowed accelerating the mechanical alloying process, i.e., the Ti6Si2B phase was formed during heating at lower temperatures than in case of titanium as starting material. As previously observed, the decomposition reaction of the titanium hydride occurred near 550 degreesC. Powder (TiH2)-22.2Si-11.1B sample milled for 90 h presented very fine particle size lower than 20 nm. The ternary Ti6Si2B phase was formed in powder Ti-22.2Si-11.1B samples after heat treatment. Traces of Ti and Ti5Si3 were also detected.

The present work reports on the syntheses of TiB and TiB2 by high-energy mechanical milling from high-purity elemental powders: Ti (99.9 wt.-%, spherical, -150 mesh) and B (99.5 wt.%, irregular, -40 mesh). Titanium hydride (99.7 wt.-%, chip) was also used in place of titanium to produce TiB. The high-energy milling was carried out in a planetary ball mill under high-purity argon atmosphere using a ball/powder weight ratio of 2:1, milling speed of 150 rpm, stainless steel vial (225 mL) and high-Cr hardened steel balls (10 mm of diameter). The powders were characterized by means of X-ray diffraction (XRD), scanning electron (SEM) and transmission (TEM) microscopes, and differential scanning calorimetry (DSC). TiB was successfully produced after heating of mechanically alloyed Ti-50at.%B and TiH2-50at.%B powders. The decomposition of the titanium hydride occurred during heating in the temperature range 500 to 600 degreesC. TiB2 was Er also formed after heating at 1100 and 1200 degreesC.

Solid state reactions induced by mechanical alloying of high-purity elemental powder mixtures of Ta and Si with atomic compositions of Ta-25%Si, Ta-33.3%Si, Ta-37.5%Si, and Ta-66.6%Si were carried out using a planetary Fritsch P-5 ball mill and stainless steel vial (225 mL). Elemental powder mixtures and hardened steel balls (10 mm diameter) were placed in the vial in an Ar-flushed glove box to avoid contamination. The mass of the powder charge per compound was close to 40 g and the mass ratio of balls to powder was 10:1. The starting and milled materials were characterized by means of X-ray diffraction (XRD), scanning (SEM) and transmission (TEM) electron microscopy, and differential scanning calorimetry (DSC). A supersaturated solid solution of Si in Ta was achieved in powder Ta-25%Si, Ta-33.3%Si and Ta-37.5%Si samples milled for 40 h while Si crystallites were also found in powder Ta-66.6%Si sample. The nanocrystalline Ta3Si, Ta2Si, Ta5Si3, and TaSi2 phases were successfully produced after milling for 40 h and further heat treatment.

Recently, the existence of a new intermetallic ternary phase, with a composition close to Ti6Si2B, was observed in the Ti–Si–B ternary system. The aim of this work is to identify the phase transformations during the oxidation experiments in air of Ti–Si and Ti–Si–B alloys containing Tiss+Ti5Si3 (eutectic), Tiss+Ti6Si2B+Ti5Si3 (eutectic) and Tiss+Ti6Si2B (after heat treatment at 1250°C for 16h). The alloy ingots were produced in an arc-melting furnace using water-cooled copper hearth and a non-consumable tungsten electrode gettered by titanium. In this sequence, oxidation experiments in air were carried out at 900 and 1100°C for 12, 24 and 48h. Samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and microanalysis via wave-length dispersive spectrometry (WDS). After oxidation experiments in air at 900°C during 48h, the following phases of the Ti–Si, Ti–B, Ti–Si–B systems were observed in the microstructures of the studied alloys: Tiss+Ti3Si in the binary eutectic (Tiss+Ti5Si3), Tiss+Ti3Si+Ti6Si2B in the ternary eutectic (Tiss+Ti6Si2B+Ti5Si3), and Tiss+Ti6Si2B in the two-phase heat-treated alloy (Tiss+Ti6Si2B). In all the alloys, the scale was composed of an outer layer of coarse grain TiO2 (rutile), an intermediate layer of a mixture of fine-grained TiO2 and SiO2 (tridymite) and other nitrite phases, and an inner layer formed by the TiSi and TiSi2 phases. Phases of Ti–Si, Ti–B and Ti–Si–B systems were not observed after oxidation experiments in air at 1100°C for 48h, due to the effects of atmospheric contamination.