PSI - Issue 59

V.V. Lytvynenko et al. / Procedia Structural Integrity 59 (2024) 372–377 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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such as thermo-mechanical treatment and annealing, a novel approach started to gain popularity: surface treatment using high-intensity energy fluxes, including ion, electron, photon, and plasma beams. These methods induce complex processes leading to structural-phase transformations. Also, they are considered as testing methods. Another aspect of application domain, they can be tools to create intermediate layers between contacting surfaces, for example, as studied by Martsynkovskyy (2019) using electric spark alloying method. When materials are exposed to intense energy fluxes, incl. high-current electron beams (HCEB), various simultaneous effects occur, including radiation-induced effects (defect formation, chemical activation), thermal effects (phase transformations, local melting, annealing, and recrystallization), shock-wave effects (dispersion of irradiated material, densification), and electrodynamic interactions (charge-current reflection, electric field generation). The irradiation of solid materials with intense pulses results in the removal of substance from the material's surface, a phenomenon known as ablation. This phenomenon finds widespread use in various applications for surface modification, spanning from macro- to nanoscales. During this interaction, various processes can occur, including melting, vaporization, sublimation, plasma and neutral vapor ejection, and grain ejection from the surface. Typically, we describe these effects as ablation process. Ablation is a multifaceted phenomenon with broad implications, and its study continues to be of great importance in materials science and various technological fields. The diversity of these ablation processes is typically determined by the type of bombarding particles, specific power densities, and the energy of the beam, e.g., see Krasheninnikov (2010). The particle penetration depth into the irradiated material determines the specific energy deposition. Comparing the efficiency of electron, ion, and laser irradiation, electron irradiation stands out with a higher coefficient of useful action, despite causing lower levels of damage than ion irradiation, Pogrebnjak (2000). In contrast, photon beams cause significantly less damage than electron beams, see Lyu Peng (2020). The advantages of electron irradiation include lower energy cost per unit, the ability to treat large areas, and high energy absorption in materials. Despite a wide range of materials, irradiation types, and conditions under investigation, common themes emerge, including collective perturbations of electronic and atomic subsystems in metals and the complex interplay of radiation, thermal, and mechanical fields, for instance in Hao Sengzhi (2007). Many effects are observed at intensities and fluxes significantly exceeding critical values, leading to phenomena such as anomalous strengthening of metals. In this study, our focus lies on investigating transformations in the homogeneous material, specifically the industrial titanium alloy VT1-0, induced by an intense microsecond relativistic electron beam. A deeper understanding of processes occurring during the ablative regime could be harnessed for the development of new functional materials. 2. Materials & Methods Irradiation of a square-shaped, 2 mm thick sample made of VT1-0 titanium alloy was performed using a hollow high-current electron beam in the TEMP A accelerator (NNC Kharkov Institute of Physics and Technology, NAS of Ukraine). The VT1-0 wrought alloy is a technically pure titanium (Ti > 99.2 wt.%), with traces of Al, Fe, C, Si. The beam had a beam current around 2 kA, electron energy 0.35 MeV, and a single pulse duration around 5 µs. The irradiation of the target was carried out in a vacuum chamber at a pressure of 10 -4 to 10 -5 Torr. The sample’s activation in terms of residual radioactivity of the sample was negligible. The inner radius of the beam was approximately 1.5 cm, the max outer radius of the hollow exposure was around 2.3 cm, while most of exposure coming into the first 5 mm from inner radius. The size of the plate exceeded the characteristic dimensions of the irradiation region. The plate was tightly screwed to the accelerators collector to have a rigid contact to prevent rupture of the sample due to plastic deformations. For this experiment, the sample target was irradiated with a single pulse. Metallographic investigations were performed using an optical microscope MIM-8M. Fractographic analyses of fractures in irradiated and non-irradiated samples of VT1-0 alloy were conducted using a scanning electron microscope JEOL JSM-840. The fractured of the sample target were done after cooling with liquid nitrogen. Modeling was conducted using the finite element and finite difference approach presented elsewhere by Klepikov (2015), Donets (2022). That theoretical model was developed based on the principles of weakly coupled thermo plasticity. The numerical model is built on top of the hyperbolic Maxwell – Cattaneo – Lykov law for heat conductance and the weakly coupled dynamic theory of thermoelasticity. The numerical model was implemented in