Design, manufacture, and characterization of a novel Ti-based nanocrystalline alloy

Abstract

A novel titanium-based alloy with low density, high hardness, and corrosion resistance was manufactured and characterized in this paper. The Ti60Ni9Fe8Co8Si15 alloy was created from its elemental components and subjected to further manufacturing. To reach a homogeneous phase, the samples were broken into small pieces and were repeatedly re-melted with arc-melting. This base alloy was further processed to manufacture an amorphous/nanocrystalline material by ball milling followed by high-pressure torsion (HPT). For subsequent characterization, X-ray diffraction (XRD), pycnometer densitometry, scanning electron microscopy (SEM) with X-ray energy dispersive spectroscopy (EDS), and hardness measurements were performed. X-ray diffractometry confirmed the formation of a amorphous/nanocrystalline structure, as most of the characteristic peaks related to the crystalline phase disappeared or flattened after ball milling. In accordance, the hardness of the manufactured samples increased by nearly 50 HV compared to the base alloy. The density of the final alloy was measured to be 4.125 g/cm3, with a hardness of 762 ± 39 HV, which confirms that an exceptionally light and, at the same time, hard material was manufactured. In order to distinguish the effects of elemental composition and manufacturing on the measured properties of our alloy, a similar Ti-based alloy with a different elemental composition (Ti47Cu40Zr7.5Fe2.5Sn2Si1) was also prepared with the same proposed manufacturing process. This reference composition resulted in significantly lower hardness (489 ± 31 HV) at a significantly higher density (5.767 g/cm3).