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3. Radiation

Radiation tolerance (1) ufg FeCrNi; (2) Ag/Ni multilayer; (3) nc Fe; (4) thermal stability of ufg FeCrNi; (5) ufg ODS alloy; (6) Cu/V nanolayer size dependent; (7) Cu/V nanolayer fluence dependent
(1) ufg FeCrNi
(2) Ag/Ni multilayer




(3) nanocrystalline Fe



(4) thermal stability of ufg FeCrNi


(5) ufg ODS alloy





(6) 
size dependent of 
Cu/V nanolayer 






(7) fluence dependent of Cu/V nanolayer

Enhanced radiation tolerance of ultrafine grained Fe-Cr-Ni alloy

C. Sun, K. Y. Yu, J. H. Lee, Y. Liu, H. Wang, L. Shao, S. Maloy, K. Hartwig,  X. Zhang, Journal of Nuclear Materials, 420 (2012):235-240.


Highlights:
  • Helium bubbles and dislocation loops were observed in helium irradiated coarse-grained Fe-Cr-Ni alloy. 
  • The overall density of helium bubbles and dislocation loops were reduced by grain refinement. 
  • The ultrafine grained microstructure alleviated radiation-induced hardening.





Comparisons of radiation damage in He ion and proton irradiated immiscible Ag/Ni nanolayers 

K.Y. Yu, Y. Liu, E. Fu, Y. Wang, M. Myers, H. Wang, L. Shao, X. Zhang,  Journal of Nuclear Materials , in press



Highlights:
  • Reduced helium bubble density and hardening in helium irradiated films.
  • Non-size dependent radiation hardening in proton irradiated films.
  • CLS model to interpret hardening mechanism




Radiation damage in helium ion irradiated nanocrystalline Fe 

K.Y. Yu, Y. Liu, C. Sun, H. Wang, L. Shao, E.G. Fu, X. Zhang, Journal of Nuclear Materials, 425 (2012) 140-146. 



Highlights:
  • Reduced helium bubble density and radiation induced hardening
  • Stress state related hardening mechanism
  • Sink effect of grain boundaries





Thermal stability of ultrafine grained Fe-Cr-Ni alloy

C. Sun, Y. Yang, Y. Liu, K. Hartwig, H. Wang, S. Maloy, T. Allen, X. Zhang, Materials Science and Engineering, A, 542 (2012):64-70. 


Highlights
  • High volume of high angle grain boundaries were produced by Equal Channel Angular Pressing technique. 
  • Abnormal grain growth occurred at ~873 K, followed by normal grain growth at higher temperature. 
  • Average activation energy of grain growth at temperature from 873 to 1073 K is  ~ 207 kJ/mol.






Microstructure refinement and strengthening mechanisms of a 12Cr ODS steel processed by equal channel angular extrusion

M. Song, C. Sun, J. Jang, C.H. Han, T. K. Kim, K. T. Hartwig, X. Zhang, Journal of Alloys and Compounds, 577(2013) 247–256. 

Highlight: 

The first successful severe plastic deformation of 12Cr ODS steels. 
Significantly refined and homogeneous microstructure in ODS steels.
Shear stress induced drastic variation of geometry of Y2O3 nanoparticles.
Strengthening arising primarily from grain refinement.









Interface enabled defects reduction in helium ion irradiated Cu/V nanolayers

E.G. Fu, A. Misra, H. Wang, Lin Shao, X. Zhang


Highlight
  • Sputter-deposited Cu/V nanolayer films with individual layer thickness, h, varying from 1 to 200 nm were subjected to helium (He) ion irradiation at room temperature. 
  • At a peak dose level of 6 displacements per atom (dpa), the average helium bubble density and lattice expansion decrease significantly with decreasing h. 
  • The magnitude of radiation hardening decreases with decreasing individual layer thickness, and becomes negligible when h is 2.5 nm or less. 
  • This study indicates that nearly immiscible Cu/V interfaces spaced a few nm apart can effectively reduce the concentration of radiation induced point defects. 
  • Cu/V nanolayers possess enhanced radiation tolerance, i.e., reduction of swelling and suppression of radiation hardening, compared to monolithic Cu or V.


Fluence dependent radiation damage in Cu/V nanolayers

E.G. Fu, H. Wang, J. Carter, Lin Shao, Y.Q. Wang & X.
Zhang

Highlight
  • We have explored the capacity of Cu/V interfaces to absorb helium ion radiation-induced defects spanning a peak damage range of 0.6–18 displacements per atom (dpa). 
  • The study provides evidence of alleviated nucleation of He bubbles in the multilayer films from Cu/V 50nm to Cu/V 2.5 nm. 
  • Peak bubble density increases monotonically with fluence, and is lower in multilayers with smaller individual layer thickness. 
  • Radiation hardening decreases with decreasing layer thickness and appears to reach saturation upon peak radiation damage of 6 dpa.