An exploratory study on biocompatible Ti-6Mn-4Mo alloy manufactured by directed energy deposition

Titanium is a widely used metal in biomedical applications due to its low toxicity, but its mechanical properties need to be tailored for different applications. Efforts are called for to search for effective and yet non-toxic elements to be alloyed with Ti to improve its strength. Fitting in this category, Mn and Mo are two such alloying elements. In this study, Ti-6Mn-4Mo alloy was manufactured by laser-directed energy deposition (DED) through in situ alloying of Ti, Mn, and Mo elemental powders. This study was intended to not only demonstrate for the first time the printability of the Ti-Mn-Mo ternary system by laser DED but also investigate the basic mechanical properties and corrosion resistance of the obtained alloy. Under the as-built condition, the alloy consisted mainly of ß phase, while after heat treatment it was transformed into α phase. The average ultimate tensile strength under as-built condition was 706.0 MPa, lower than similar alloys from conventional methods. However, the average hardness reached 421.1 HV for the as-built condition, much higher than the similar alloys made through conventional methods. On the other hand, the corrosion resistance of the obtained alloy was found to be relatively low compared to similar alloys produced with traditional methods. In addition, heat treatment was not able to significantly change the tensile properties or the corrosion resistance. In essence, the exploratory study indicates that the DED-produced Ti-Mn-Mo alloy could be deposited without cracks and major voids, and shows that its high hardness and modulus are attractive to applications for high wear resistance. However, further investigation is needed to improve strength, ductility, and corrosion resistance of the alloy.