Effect of Mo Content on Microstructure and Properties of Laser Additive Manufactured TC4 Alloy

Abstract:

Due to the excellent mechanical properties and outstanding biocompatibility, TC4 titanium alloy has been widely used in the aerospace and medical device field. Laser additive manufacturing (LAM) is an important technique for fabricating titanium alloys. The presence of large numbers of columnar crystals and acicular martensite in additive manufactured TC4 titanium alloy results in anisotropy and reduced plasticity. In this work, molybdenum (Mo) was added to tailor the microstructure and properties of additive manufactured TC4 titanium alloy, with a specific focus on the effect of Mo content. The results show that an appropriate Mo content can effectively refine the grains. Furthermore, with the addition of Mo element, the TiAl₃ phase is gradually precipitated from the alloy matrix, and its content is increased with the increase in Mo content. When the Mo content reaches 8wt%, a fine and dispersed lamellar structure is distributed in the alloy, and the β-phase content increases sharply. In addition, the maximum degrees of grain refinement and dislocation density are obtained. As Mo content increase from 0 to 10wt%, the tensile strength, hardness and corrosion resistance of the alloy increase first and then decrease, whereas the elongation shows the opposite trend. Concurrently, the Young's modulus gradually decreases. When Mo content is 8wt%, the alloy achieves the best mechanical properties: a tensile strength of 1065.6 MPa, an elongation of 11.5% and Young's modulus of 55.4 GPa. Additionally, its corrosion resistance is improved. Overall, TC4-8Mo sample has excellent mechanical properties and superior corrosion resistance, demonstrating high potential for use in human medical implant.