Effect of powder preparation methods on Ti31 alloy powders for additive manufacturing

【Objective】 In the field of metal additive manufacturing, the properties of raw material powders are one of the key factors affecting the quality of printed parts. Ti31 titanium alloy is a Ti-Al-Mo-Ni based near α titanium alloy with high-temperature resistance, corrosion resistance, and hydrogen embrittlement resistance, which has been widely applied in marine engineering and nuclear industries. However, at present, there are relatively few research on the preparation of Ti31 titanium alloy powders and the performance of printed sample. Therefore, it is necessary to conduct relevant research to clearly explain the effect of powder preparation methods on Ti31 alloy powders and printed parts.
【Method】 Ti31 titanium alloy powders were prepared by electrode induction gas atomization (EIGA) and plasma rotating electrode process (PREP), respectively. The characteristics of powders including chemical composition, morphology, particle size distribution of EIGA and PREP powders were compared. The vibration sieving method was used to classify the particle size of the obtained powder under inert gas protection, and Ti31 powder with a particle size of 15-53 μm was obtained after sieving. The selective laser melting (SLM) adaptability of the powders was analyzed.Ti31 samples were prepared using with MT-450 equipment and TC4 titanium alloy as the printing substrate. The substrate surface was cleaned and dried before printing. The forming scanning strategy was strip scanning, with adjacent layers rotated 67 °. The Ti31 printed samples were solution treatmented, with a process of holding at 800 ℃ for 2 hours and then air cooling to room temperature.SLM printed samples were subjected to chemical composition testing and morphology obcevation after polishing. Tensile tests of Ti31 printed samples after heat treatment were conducted at room temperature, with the tensile samples taken from the X forming direction.
【Result】 The results show that the Ti31powder produced by two methods exhibit low non-metallic element content, and the main phase of the powders is α-Ti hexagonal close-packed (hcp) crystal structure. Furthermore, compared with EIGA powder, the PREP powder exhibits lower oxygen content, higher sphericity, better flowability, and lower hollow powder rate. The main phase of Ti31 powder prepared by EIGA method and PREP method is α-Ti hcp crystal structure.The chemical composition and tensile properties at room temperature of the printed Ti31 alloy meet the requirements of Ti31 forging standard. The EIGA-fabricated specimens exhibit higher ultimate tensile strength and yield strength, while the PREP-fabricated specimens show superior elongation and reduction.
【Conclusion】 The Ti31 powder prepared by EIGA and PREP methods was subjected to SLM additive testing, and the room temperature tensile properties of the Ti31 printed samples met the performance indicators of Ti31 forging samples, verifying the good compatibility between Ti31 powder and SLM process.