Atomistic simulation of crack propagation in single crystal tungsten under cyclic loading

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Shi-fang Xiaoa) and Hui-qiu Deng Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082, China

Lei Ma College of Physics and Electronic Science, Hunan University of Arts and Science, Changde 415000, China

Wangyu Hub) College of Materials Science and Engineering, Hunan University, Changsha 410082, China (Received 23 December 2016; accepted 13 March 2017)

The propagation of a pre-existing center crack in single crystal tungsten under cyclic loading was examined by molecular dynamics (MD) simulations at various temperatures. The results indicated that the deformation mechanism and fracture behavior at crack tip were differences for variously oriented cracks. The [001](010) crack propagated as the form of the formation of slip, while the deformation mechanisms of [101](101) crack were blunting voids at 300 K. At higher temperature, many more slip systems were activated resulting in the change of mode of crack propagation. Simulated results showed that the effect of temperature on deformation mechanism and fracture behavior of [001](010) crack was more sensitive than that of [101](101) crack. Meanwhile, the influence of a 5h310i{110} model grain boundary (GB) on crack propagation was also discussed. Detailed analysis showed that the grain boundary resisted the crack growth by changing the deformation mechanisms and the path of crack propagation at crack tip before the crack reached the grain boundary, and had an important influence on the crack growth rate.

I. INTRODUCTION

Tungsten is remarkable for its robustness, high heat conductivity, and low sputtering erosion, and it has the highest melting point for all the nonalloyed metals. Due to the above advantages, tungsten becomes one of the important candidates of the plasma facing materials (PFM), and is most probable to be used as the first wall material in the future fusion reactor. The properties of tungsten, such as recrystallization behavior, the ductileto-brittle transition and thermal stability, have been investigated experimentally and theoretically.1–6 However, the study on the fatigue crack growth in tungsten is still rather poor. As PFM, tungsten is supposed to bear high thermal loads, which could induce high thermal stresses and the formation of crack. The crack propagation in tungsten will cause the fatal destruction of the components. Therefore, it is important to understand the fracture mechanisms of tungsten due to the crack propagation. Recently, the fatigue crack extension behavior has been widely discussed by molecular dynamics (MD) Contributing Editor: Susan B. Sinnott Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2017.114

simulations. Much research shows that the crack propagation and dislocation emission are influenced by the crack orientation.7–11 In addition, there are many other factors influencing the mode of crack growth. Lee et al.12 analyzed the influence of grain boundary property variation on rupture resistance of pol

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