Continuous Electron Beam Post-Treatment of EBF3-Fabricated Ti–6Al–4V Parts

Abstract

In the present study, the methods of optical, scanning electron, and transmission electron microscopy as well as X-ray diffraction analysis gained insights into the mechanisms of surface finish and microstructure formation of Ti–6Al–4V parts during an EBF3-process. It was found that the slip band propagation within the outermost surface layer provided dissipation of the stored strain energy associated with martensitic transformations. The latter caused the lath fragmentation as well as precipitation of nanosized β grains and an orthorhombic martensite α″ phase at the secondary α lath boundaries of as-built Ti–6Al–4V parts. The effect of continuous electron beam post-treatment on the surface finish, microstructure, and mechanical properties of EBF3-fabricated Ti–6Al–4V parts was revealed. The brittle outermost surface layer of the EBF3-fabricated samples was melted upon the treatment, resulting in the formation of equiaxial prior β grains of 20 to 30 μm in size with the fragmented acicular α′ phase. Electron-beam irradiation induced transformations within the 70 μm thick molten surface layer and 500 μm thick heat affected zone significantly increased the Vickers microhardness and tensile strength of the EBF3-fabricated Ti–6Al–4V samples.

Electron-Beam Surface Treatment of Metals and Alloys: Techniques and Trends

“…Both techniques significantly differ from each other, where the main difference is the heating and cooling rate. In the case of pulsed EBT, this rate can reach values of 10 9 K/s [12,13], while in the continuous mode it is about 10 5 K/s [14], which leads to the different structure and functional properties of the processed materials. In both types of techniques, the energy parameters of the beam are of major importance and are as follows: The acceleration voltage U [V]; the beam current I [A] and the beam diameter d [15].…”

Improving mechanical properties of wire‐based EBAM Ti‐6Al‐4V parts by adding TiC powders

“…This problem cannot be completely solved by varying combinations of the building parameters. As was shown in Panin et al, 14 wire‐based EBAM Ti‐6Al‐4V wall‐shaped samples measuring 85 × 5 × 70 mm were characterized by large columnar prior β‐grains with a diameter of 500 to 1000 μm, while their length reached several millimeters. The current results evidence that the variation of AM strategy as well as water cooling of the substrate does not result in a significant decreased in average size of prior β‐grains.…”

Влияние охлаждения подложки на микроструктуру и фазовый состав изделий из титанового сплава Ti-6Al-4V, полученных методами аддитивных технологий

“…Параметры обработки импульсным или непрерывным электронным пучками подробно описаны в [11]. Независимо от режима охлаждения подложки методами ПЭМ фаза β-Ti наблюдается в виде прослоек по границам пластинчатых зерен α-Ti, унаследованных от α ′ -мартенсита [12]. В части зерен α-Ti наблюдаются как больше так и малоугловые границы с нанокристаллическими фазами β-Ti и α ′′ -Ti (рис.…”