Microstructural characterization of the Ti-30Nb-6Sn alloy synthesized by mechanical alloying

Abstract

Titanium and its alloys are used as technical materials mainly because of the low density (ρ = 4.5 g cm-3) of Ti at technically useful levels of mechanical properties, and the formation of a passivating, protective oxide layer in air, which leads to a pronounced stability in corrosive media and at elevated temperatures.[1] The great interest of titanium alloys in the biomedical sector is well known due to their suitable characteristics for biomaterials compared to other metallic materials. However, there are still some concerns regarding titanium alloys such as the high Young’s modulus which is superior to that of human bone, the design of β–Ti alloys emerges as a response to the necessity of improving other poorer aspects such as stiffness. β–Ti alloys have low Young’s modulus while maintaining or enhancing the material strength by incorporating biocompatible elements such as Nb or Mo which makes them ideal for biomedical applications. Furthermore, Mo and Nb exhibit complete solubility in Ti above 882°C which allows a microstructural change and thus, the modification of their properties[2]. Mechanical alloying (MA) is a solid-state powder processing technique involving repeated welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Originally developed to produce oxide-dispersion strengthened (ODS) nickeland iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from blended elemental or prealloyed powders. The non-equilibrium phases synthesized include supersaturated solid solutions, metastable crystalline and quasicrystalline phases, nanostructures, and amorphous alloys[3].