Dislocation driven nanosample plasticity: new insights from quantitative in-situ TEM tensile testing.

Area of Science:

• Materials Science
• Solid Mechanics
• Physical Metallurgy

Background:

• Understanding small-scale plasticity is crucial for materials design.
• Dislocation behavior near surfaces significantly influences material properties.
• Previous studies lacked detailed mechanisms for dislocation activity in near-surface regions.

Purpose of the Study:

• To quantitatively investigate intrinsic dislocation mechanisms near free surfaces.
• To elucidate the role of dislocations in small-scale plasticity of nickel.
• To understand the formation and operation of dislocation sources.

Main Methods:

• Utilized a novel sample preparation combining twin-jet electro-polishing, in-situ TEM heating, and focused ion beam (FIB) milling.
• Achieved an almost FIB damage-free single crystal nickel sample.
• Employed in-situ transmission electron microscopy (TEM) for real-time observation.

Main Results:

• Small-scale plasticity is controlled by the conversion of tangled dislocations into stable single arm sources (SASs).
• Observed strain hardening attributed to the decreasing length of operating SASs.
• Demonstrated the impact of source shortening on intermittent plastic flow.

Conclusions:

• Dislocation source-controlled plasticity and mechanical size effects are significantly influenced by SAS operation.
• The findings offer critical insights into the fundamental mechanisms governing plasticity in metals.
• The novel sample preparation method enables advanced in-situ studies of dislocation dynamics.