Details

Autor(en) / Beteiligte

• Li, N.
• Nastasi, M.
• Misra, A.

Titel

Defect structures and hardening mechanisms in high dose helium ion implanted Cu and Cu/Nb multilayer thin films

Ist Teil von

• International journal of plasticity, 2012-05, Vol.32-33, p.1-16

Ort / Verlag

Kidlington: Elsevier Ltd

Erscheinungsjahr

2012

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• ► Uniform distribution of He bubbles throughout the films. ► Significant hardening due to bubbles is observed large layer thickness films. ► For the finest multilayers (layer thickness ≤5nm), the hardening is suppressed. Helium (He) exerts a significant influence on the mechanical behavior of irradiated materials. The microstructural evolutions and hardening mechanisms of pure 1μm thick Cu film and Cu/Nb multilayers of individual layer thickness of 70nm, 5nm and 2.5nm were investigated after 1at.% and 7at.% He ion implants at room temperature. Implantation of 7at.% He produces a uniform dispersion of bubbles throughout the film in all samples and bubble pressure increases and volume fraction decreases with reducing layer thickness. For 5nm layer thickness approximately 32% He atoms are trapped at Cu–Nb interface, grain boundaries or dislocations in the form of He-vacancy clusters, which cannot be detected by electron microscopy. For a 1 at.% He implantation, He bubbles are barely detectable in Cu/Nb multilayers with 5nm individual layer thickness or less, suggesting the extraordinary capability of the Cu–Nb interface in absorbing and annihilating point defects. Hardness measurement indicates for coarse multilayers (h≥70nm) and pure Cu, the hardening from He bubbles is significant and increases with increasing He content, which can be described by Orowan hardening mechanism. However, when h is small (h≤5nm), the hardening is significantly mitigated, regardless of He concentration. The strengthening mechanism is dependent upon the resistance of the defect loaded interface to the transmission of single dislocation.