Effect of molybdenum on structure, microstructure and mechanical properties of biomedical Ti-20Zr-Mo alloys

Abstract

Titanium has an allotropic transformation around 883°C. Below this temperature, the crystalline structure is hexagonal close-packed (α phase), changing to body-centered cubic (β phase). Zirconium has the same allotropic transformation around 862°C. Molybdenum has body-centered cubic structure, being a strong β-stabilizer for the formation of titanium alloys. In this paper, the effect of substitutional molybdenum was analyzed on the structure, microstructure and selected mechanical properties of Ti-20Zr-Mo (wt%) alloys to be used in biomedical applications. The samples were prepared by arc-melting and characterized by x-ray diffraction with subsequent refinement by the Rietveld method, optical and scanning electron microscopy. The mechanical properties were analyzed by Vickers microhardness and dynamic elasticity modulus. X-ray measurements and Rietveld analysis revealed the presence of α' phase without molybdenum, α'+α″ phases with 2.5wt% of molybdenum, α″+β phases with 5 and 7.5wt% of molybdenum, and only β phase with 10wt% of molybdenum. These results were corroborated by microscopy results, with a microstructure composed of grains of β phase and lamellae and needles of α' and α″ phase in intra-grain the region. The hardness of the alloy was higher than the commercially pure titanium, due to the action of zirconium and molybdenum as hardening agents. The samples have a smaller elasticity modulus than the commercially pure titanium.

Characterization of chemically treated Ti-Zr system alloys for dental implant application

“…Herein, the developed alloys presented the elemental concentrations very close to the stoichiometric values without presenting contaminants, which demonstrate their good quality [11,21,26]. Few differences were observed for the double etched surface as the increase of Zr content.…”

Development of binary and ternary titanium alloys for dental implants

“…In this work, the proportions found of the alloying elements showed a small difference from the nominal composition. However, the Zr and Nb concentrations were close to stoichiometric values [17], demonstrating greater incorporation during the melting process. This small difference can be attributed to the excluded vibrational contribution to the theoretical formation energy and mixing of unwanted interstitial elements (mainly oxygen) during alloy production [53].…”

“…Experimental Ti alloys without the presence of Al and V are being processed and studied to achieve these properties [17]. Zirconium (Zr) and niobium (Nb) elements have attracted much special attention [18].…”

Development of novel Ti-Mo-Mn alloys for biomedical applications

“…The increase in density is related to the density of the www.nature.com/scientificreports www.nature.com/scientificreports/ elements that compose the alloys. The density of molybdenum (10.28 g/cm³) is greater than that of the other alloying elements, titanium (4.54 g/cm³) and manganese (7.44 g/cm³) 25,26 .…”