Study on Microstructure Uniformity of Ti-6Al-4V through Electron Beam Additive Manufacturing

Selective electron beam melting technology (SEBM) has many advantages, such as high power, a high energy utilization rate, and a fast-forming speed. Ti-6Al-4V is one of the most used materials in α + β titanium alloys, and it has broad application prospects in various fields, such as aerospace. Small-size Ti-6Al-4V parts are widely used, so the microstructure and performance analysis of small-height parts molded by additive manufacturing is the focus of research. In this paper, the titanium alloy Ti-6Al-4V aerosolized ultra-low clearance powder was processed using SEBM technology, and the 10 mm high titanium alloy was obtained. The microstructure, Vickers hardness, nanoindentation, and tensile properties of the alloy were tested. The results show that the hardness of Ti-6Al-4V samples prepared using electron beam selective melting is in the range of 275-330 HV, and the microstructure, hardness, and nanoindentation are homogeneous. Further tensile property analysis shows that the tensile strength of the samples in different directions is 977 MPa and 957 MPa, respectively, the elongation after fracture has little difference, and the tensile properties parallel to the direction of additive manufacturing and perpendicular to the direction of additive manufacturing have little difference; they also conform to the uniformity. The reason why the mechanical properties and fractures of the samples in both directions are similar is that there are many orientated columnar crystals along the XOZ plane, and these columnar crystals fracture in the same way under the action of stress. In this paper, we mainly focus on and verify the uniformity of microstructure and properties of Ti-6Al-4V samples with small height in additive manufacturing in different directions. This work is helpful for engineers to better understand the microstructure evolution process in the SEBM process, and it is helpful for process control, improvement, and optimization in the SEBM process.