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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Fig. 4. (a) Calculated profiles of cooling versus energy release depth into the sample, where 1 – at ~6 µs ; 2 – 10 µs; 3 – 20 µs (after the star t of irradiation). A – if we consider no heat exchange on the front boundary (T x=0 = 20), and B – when there is a heat exchange with a source. The near-surface area was formed primarily through the condensation and solidification of the melt on the surface. Observations revealed that the depth at which the cooling rate reaches zero, aligns with the thickness of the quenched re-melted zone. This alignment suggests that the predominant contributor is the rapid cooling rate. The depth of the near-surface high temperature gradient corresponds to the quenched zone's thickness for both conditions. The demarcation between the quenched zone and the heat-affected zone indicates a distinct shift into an isothermal region which then transfers into area of high gradients. Rapid cooling may have provoked formation of α ׳ martensitic microstructure as it was observed by Zhang (2011) in a pure titanium using a low-energy HCEB . In their research, they’ve noticed a significant increase in hardness in the processed layer (more than 60%). Ourselves, we observed hardness increase by around 30% as reported previously in Klepikov (2015). However, low-energy beams modify a volume only up to a few µm in depths, while relativistic beams penetrate more deeply into a bulk and reduce the strengthening microstructural effects. In case of nanosecond relativistic beams as in Lavrientiev (1999), a high pressure ω phase forms due to high compressive stress at the surface. Considering the treatment of VT-1 alloy with irradiation by high-energy charged particles as a means to study its resistance to extreme energy fluxes, such as a current disruption in a thermonuclear reactor, it should be noted that the formed surface layer may subsequently be vulnerable to the effects of neutron flux and high temperatures, as is typical for even radiation-resistant compounds as reported by Slisenko (2021). 4. Conclusions The study presented details about the modifications induced by intense electron beam irradiation (5- µs, 0.35 MeV, 2 kA) in ablative mode in the Titanium alloy VT1-0. Experimental analyses and numerical calculations shown the insights into dynamics and results of irradiation. Substantial material changes were revealed, emphasizing the formation of a distinctive multi-layered structure consisting primarily of quenched re-melted near-surface zone and heat-affected zone. The HCEB irradiation led to embrittlement of the material compared to the initial reference material. The described approach enhances comprehension of intense electron beam-induced modifications in metallic targets. Acknowledgements The research presented in this article was financially supported by the Ukrainian government budget program «Government support for priority scientific research and scientific & technical (experimental) developments» (budget financial Code 6541230) and Simons Foundation Program: Presidential Discretionary-Ukraine Support Grants, Award No 1030287. Also, it was supported by the stipend of the President of Ukraine for Young Scientists, granted for the corresponding author.