Optimization of tensile properties of a hierarchical structured TiZrAlV alloy by proton irradiation
Introduction
The irradiation of high-energy particles usually leads to the deterioration of mechanical properties of materials by introducing high-density crystal defects, e.g. point defects and aggregated defect clusters. To suppress the deterioration of mechanical properties and ensure the safety of nuclear plants and spacecrafts served in irradiation environment, the strategy of using nanostructured materials has been proposed due to their high-density grain boundaries and phase interfaces that act as sinks to point defects [1]. However, the application of nanostructured materials was limited by their poor ductility. Fortunately, a concurrent of high strength and ductility was achieved by introducing coarse grains into nanostructured matrix to form a hierarchical structured (HS) material, in which fine grains contribute to strength and coarse grains contribute to ductility [2]. Moreover, high-density grain boundaries and phase interfaces in HS materials may act as sinks to irradiation-induced point defects, indicating a potential of inhibiting the deterioration of mechanical properties [3]. In this study, we report an abnormal proton irradiation-induced optimization of tensile properties of a HS-TiZrAlV alloy, and the mechanism governing the phenomenon has been discussed.
Section snippets
Experiment
To produce HS materials, the deformed 40.2Ti-51.1Zr-4.5Al-4.2V (wt%; referred to as TiZrAlV) sheets were subjected to recrystallization annealing (675 °C/10 min) and subsequent two-step aging (625 °C/2h+300 °C/3h) [4]. Then, the HS-TiZrAlV was treated by proton irradiation on the rolling plane using a 2*6 MV tandem accelerator in vacuum. The proton intensity is 1012–1013 cm−2 and the proton energy is 9 MeV. The temperature of the samples was kept below 100 °C during the irradiation processes using a
Results and discussion
The tensile curves of TiZrAlV before and after proton irradiation are shown in Fig. 1a. The as-prepared TiZrAlV shows an ultimate tensile strength of σb=1585 MPa and an elongation to failure of εf=7.0% (Curve A). Strikingly, after proton irradiation with a dose of 1012 and 1013 cm−2, the εf increases to 9.2% and 10.2% while the σb decreases slightly to 1533 and 1506 MPa (curves B and C), respectively. Moreover, dimple structures on the fracture surface of the irradiated TiZrAlV (inset C') are
Conclusions
An abnormal irradiation-induced optimization of tensile properties has been observed in a HS-TiZrAlV alloy, which results from the irradiation-induced lattice relaxation, and the absorption of irradiation interstitials and vacancies at high-density boundaries and phase interfaces. These results indicate the irradiation-induced deterioration of mechanical properties of materials can be alleviated or overcome using a hierarchical structure.
Acknowledgments
The authors gratefully acknowledge the financial support of the National Basic Research Program of China (No. 2010CB731606) and National Natural Science Foundation of China (Nos. 51171164, 51031004 and 51121061).
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2019, Science China Technological Sciences