RESUMO
Commercially pure titanium (cp-Ti) and Ti-6Al-4V alloy have emerged as excellent candidates for use as biomaterials in medical implants due to their high strength-to-weight ratio and biocompatibility. ß-type Ti alloys composed of non-toxic metallic elements such as niobium (Nb) have been extensively studied in order to resolve the issue of a high elastic modulus and toxicity of certain elements, particularly in Ti-6Al-4V alloy. Titanium hydride (TiH2) has recently received a lot of attention due to its densification, oxidation levels, and material costs. Powder metallurgy combined with mechanical alloying has become an attractive route for producing near-net shape components of Ti-based alloys, mainly where porosity control and better homogeneity are required. This review aims to create a platform for investigating the feasibility of producing Ti from TiH2 via a dehydrogenation process. The dehydrogenation behaviour of TiH2 is affected by variables such as sintering condition, alloying element, and particle size. The review revealed that TiH2 decomposition occurs at various temperatures (400 °C to 800 °C), resulting in the formation of several sequences of phases. Although the dehydrogenation process was unaffected, the addition of alloying elements was found to change the starting and ending temperatures of the reactions. The use of vacuum accelerates the dehydrogenation process more than argon flow. TiH2 powder with smaller particle size, on the other hand, eliminates hydrogen faster than larger ones due to the larger surface area exposed. This review also looks at the best processing conditions for getting a high concentration of ß phase in Ti-Nb alloys. ß-type titanium alloys with a low elastic modulus (10-40 GPa) similar to human bone are a potential strategy for reducing premature implant failure.
RESUMO
In this study, an in situ nanostructured copper tungsten carbide composite was synthesized by mechanical alloying (MA) and the powder metallurgy route. The microstructure and phase changes of the composite were characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. Tungsten carbide phases (WC and W2C) were only present after MA and combination of sintering. Higher energy associated with a longer milling time was beneficial for the formation of WC. Formation of W2C and WC resulted from internal refinement due to heavy plastic deformation in the composite. The solubility of the phases in the as-milled and sintered composite was described by the changes of the lattice parameter of Cu. Chemical analysis of the surface of a composite of W 4f and C 1s revealed that the increased defects introduced by MA affect the atomic binding of the W-C interaction.
RESUMO
Considering the necessity for a biodegradable implant alloy with good biocompatibility and mechanical strength, dual ceramic particles of HAP and Al2O3 were added to Mg-Zn alloy to produce a new hybrid composite using powder metallurgy. The paper reports the mechanical and corrosion behaviour of Mg-Zn/HAP/Al2O3 hybrid composites containing variable wt.% HAP and Al2O3 with 15 wt.% total ceramic content. The powders of Mg, Zn, Al2O3 and HAP were milled in a high-energy ball mill, and then compacted under 400 MPa and sintered at 300 °C. Density and compression strength increased with increasing Al2O3 content. HAP facilitated weight gain in Hanks balanced salt solution due to deposition of an apatite layer which promoted anodic behaviour with higher corrosion resistance. A hybrid composite of Mg alloy with 5 wt.% Al2O3 and 10 wt.% HAP displayed 153 MPa compressive strength, 1.37 mm/year corrosion resistance and bioactivity with a CA:P ratio of 1:1.55 and appears to be the most promising biodegradable implant material tested.
