Insights into radiation resistance of titanium alloys from displacement cascade simulations

Abstract

Radiation damage in beam window materials limits the use of high power proton beams in high energy physics research. The alloy Ti-6Al-4V is presently used as a beam window material but a prospective alternative, Ti-15V-3Cr-3Sn-3Al has been proposed. Since both these alloys contain dual phases at room temperature, we compare the radiation damage in the α and β-phases of these two materials via primary knock-on atom (PKA) cascade simulations in the 10–40 keV energy range. At PKA energies 30 and 40 keV, the number of Frenkel pairs in the ballistic stage is higher in the β-phase of Ti-6Al-4V than that in the β-phase of Ti-15V-3Cr-3Sn-3Al almost by a factor of 2. The α-phase, of both these alloys, by far outperforms the β-phases of the two alloys, both in terms of damage during the ballistic stage and in terms of the surviving defects. The average displacement threshold energy (Ed) in the α-phase of both alloys was found to be 66 eV while that in the β-phase of Ti-15-3-3 was 55 eV and in the β-phase of Ti-6-4 was 46. While the number of surviving defects is almost equal in both alloys, the vacancy and interstitial clustering mechanisms differ notably, which can impact the degree of radiation hardening and loss of ductility. Our simulations show larger vacancy and interstitial clusters form in Ti-6Al-4V as compared to that in Ti-15-3-3-3 alloy. These results indicate that Ti-15-3-3-3 alloys may be a promising candidate for next generation beam window material with a higher radiation tolerance than the existing Ti-6-4 alloy.