Research‎ > ‎

1. Nanotwins

Highlights: (1) nanotwinned Al, (2) nanotwinned Cu/Ni (3) nanotwinned Ag (4) annealed nanotwinned Ag
(1) Nanotwinned Al






(2) Nanotwinned Cu/Ni












(3) Nanotwinned Ag





(4) Thermal stability of nanotwinned Ag


Formation mechanisms of high-density growth twins in aluminum with high stacking fault energy

D. Bufford, Y. Liu, Y. Zhu, Z. Bi, Q.X. Jia, H. Wang, and X. Zhang  Materials Research Letters (2013), 51-60.


Highlight: 

High-density growth twins induced in Al via using nanotwinned Ag as a template
Three twin propagation mechanisms are identified
Twins significantly enhance mechanical strength 



A formation mechanism for ultra-thin nanotwins in highly textured Cu/Ni multilayers

Y. Liu, D. Bufford, S. Rios, H. Wang, J. Chen, J. Zhang, and X. Zhang; J. Appl. Phys. 111, 073526 (2012)


Highlights:
  • The formation of high density twins in the Cu/Ni multilayer is an effective mechanism rather than misfit dislocations to relax the elastic strain energy when h is a few nm.
  • The maximum twin thickness can be tailored to a greater extent by layer thickness. A reversal occurs when the interface becomes fully coherent. 
  • High density twins formed this way can grow into the layer constituent with relatively high stacking fault energy (Ni at here). Shear stress at the edge of twin nuclei provides necessary driving force for the formation of growth twins.


High strength, epitaxial nanotwinned Ag films

D. Bufford, H. Wang, X. Zhang,  Acta Materialia, 59 (2011) 93–101. 


Highlight: 

Epitaxial nanotwinned films with different orientations synthesized
Twin density varies with orientation
Twins induce high mechanical strength





Thermal stability of twins and strengthening mechanisms in differently oriented epitaxial nanotwinned Ag films 

D. Bufford, H. Wang, and X. Zhang, Journal of Maters Research, 28 (13), 2013.


Highlight: 

Nanotwinned Ag films show remarkable thermal stability, with <100nm spaced twins remaining after annealing to ~85% of the melting temperature
Retention of twins depends on the film orientation
Hardness reflects the small retained feature size