Effects of Fe Addition on the Phase and Mechanical Properties of Ti-15Mo Alloy

The influence of high content of Fe on the microstructure and mechanical properties of as-cast Ti-15Mo alloy is explored in this work. The alloys (binary and 3 ternaries) were melted in a commercially available Vacuum arc-melting furnace (VAR). Characterization of samples was conducted using the microstructural features of the binary alloys an Optical Microscopy (OM) and an X-ray diffractometer (XRD) to reveal microstructural features and identify present phases, respectively. Tensile and Micro-Vickers hardness tests were carried out to study mechanical properties while the fracture surface was examined using the Scanning Electron Microscope (SEM). The XRD analyses detected peaks belonging to the bcc Im3m (β-Ti) phase in binary Ti-15.05Mo alloy and β, α″ (Cmcm), and TiFe (B2) phases in ternary alloys containing Fe. The Optical microscopy revealed equiaxed β grains with additional structures or features such as needle-like structures of martensite inside the grains in Ti-15.05Mo whilst the addition of Fe resulted in equiaxed structures with dendrites inside. As a result of these dendritic structures, the ternary samples were too brittle and fragile to generate adequate tensile data. The Micro-Vickers hardness results indicated that the hardness slightly decreased at first with the addition of Fe and later increased with a further increase in Fe composition. The fracture surfaces analysis illustrated both ductile and brittle fracture in Ti-15.05Mo while only brittle fracture was observed in alloys containing Fe.