Immiscible Cu alloys effects on radiation induced creep

  noya firman dimanstein  ,  Yinon Ashkenazy  
Racah Institute of Physics,

Radiation fluxes in materials, lead to local displacements of atoms and generation of point defect fluxes, those fluxes lead to intense plastic response named creep [1]. Radiation induced creep (RIC) is a main failure mechanism in fission reactors.

The mechanism in which RIC occurs include the releasing of sessile dislocations through interactions with irradiation induced point defects [1]. Thus RIC can be reduced by the integration of high densities of sinks and traps for point defects within the material [2]. Nano-crystalline (NC) metals have a large concentration of interfaces. These interfaces serve as sinks and traps for point defects, furthermore, the interactions with abundant interfaces in NC lead to ”dislocation starvation” [3]. However, NC metals are susceptible to thermal creep, and so a fundamental question concerns their sensitivity to RIC. Molecular dynamics (MD) simulations implies that local relaxations that occur within the NC GB controls RIC dynamics [4]. However creep compliance in NC was shown to have an inverse dependence on grain size, a unique dependence which is markedly different from other GB controlled creep mechanisms.

NC metals are affected by coarsening, to stabilize the metal against coarsening it is customary to introduce immiscible materials into the matrix in production. The introduction of such immiscible atoms leads to resistance against thermal grain growth by a combined effect of GB stabilization by solute atoms as well as precipitate growth leading to Zener pinning [5]. It was shown [6] that in NC Cu-W, solute concentration has a strong effect on RIC. Specifically, at T~300, RIC rate at Cu-1%w is ~ 17 greater than RIC rate at Cu−6.5% W. We aim to use the strong effect of the immiscible matrials on RIC in NC alloys to study the microscopic mechanise of RIC in NC alloys.

[1] G. Was,Fundamentals of Radiation Materials Science: Metals and Alloys (Springer, Berlin, 2007).

[2] A. Hirata, T. Fujita, Y. R. Wen, J. H. Schneibel, and C. T. L. M. W. Chen10, Nature Materials10, 992 (2011).

[3] Z. W. Shan, R. K. Mishra, S. A. S. Asif, O. L. Warren, and A. M. Minor, Nature Materials 7, 115 (2007)

[4] Y. Ashkenazy and R. S. Averback, Nano Letters 12, 40844089 (2012).

[5] X. Zhang, J. Wen, P. Bellon, and R. S. Averback, Acta Materialia 6, 2004 (2013)

[6] K. Tai, R. S. Averback, P. Bellona, Y. Ashkenazy, and Stumphy, J. Nuc. Mater. 422, 8 (2012)