## 1 Introduction  
With the rapid development of science and technology, borosilicate glass has been widely applied in irradiated environments, including aircrafts, radioactive medicine and the disposal of high-radiation waste [1; 2; 3; 4]. Considering the nature of these applications, having a stable mechanical property is of significant importance to ensure long-term performance in nuclear technological applications. However, investigations have revealed that the radiation originated from the decay of radionuclides affects the mechanical characteristics of most conventional materials, including borosilicate glass. Therefore, investigating the irradiation-induced evolutions of the mechanical characteristics of borosilicate glass is an essential issue.  
Reviewing the literature indicates that many researchers have studied the mechanical property evolutions of ion- and electron-irradiated borosilicate glass. In order to reveal the underlying mechanisms of this issue, experiments have been carried out to study the microstructure and macrostructure changes of glass after the irradiation [5; 6; 7; 8; 9]. The obtained results showed that variations in the mechanical characteristics mainly depended on the ion species [5; 10; 11; 12]. [PERSON] et al. showed that the hardness of an equivalent non-radioactive glass decreased by 30% after Kr ion irradiation, while He ion irradiation did not affect it [5]. Accordingly, it was concluded that nuclear energy deposition is the principal factor, and that the electronic energy deposition has a negligible effect on the hardness reduction after irradiation. However, further investigations demonstrated that the induced hardness by the electronic energy deposition significantly decreased in the electron-irradiated borosilicate glass [10]. This issue may be attributed to the structural variationsoriginating from sodium migration that is induced by electron energy deposition. [PERSON] et al. carried out experiments and showed that the hardness of irradiated borosilicate glass by He and Au ions decreased by 22% and 38%, respectively [11]. Accordingly, it was inferred that both electronic and nuclear energy deposition affect the mechanical characteristics of the glass. Moreover, [PERSON] et al. showed that, when BS3 and SON68 glasses were exposed to He ion irradiation, the corresponding hardness initially decreased by 18% and 14%, respectively, and then remained constant. Meanwhile, such a reduction for Au ion irradiation was 35%. It was inferred that the hardness reduction mainly originated from the nuclear energy loss for the electronic energy loss less than 4 keV/nm [12]. These results indicate that ionic irradiation affects the mechanical property of borosilicate glass. However, the correlation between ionic irradiation and the mechanical characteristics of glass has not been expressed yet. This is especially more pronounced for the effects of electronic and nuclear processes [12]. In order to resolve these shortcomings, it is of significant importance to carry out a systematic study to clarify the detailed mechanism.  
In this regard, this study is intended to investigate borosilicate glass subjected to the external irradiation of 0.5 MeV He and 2 MeV Ar. Furthermore, the evolutions of hardness and the Young modulus before and after irradiation are analyzed through the nano-indentation measurement method. The main objective of the present study is to establish a correlation between evolutions of mechanical characteristics and ionic irradiation.