Rotatable precipitates change the scale-free to scale dependent statistics in compressed Ti nano-pillars

Area of Science:

• Materials Science
• Nanotechnology
• Mechanical Engineering

Background:

• Compressed nano-pillars exhibit crackling noise from moving dislocations, reducing plastic stability.
• This phenomenon typically follows power-law statistics due to stress drops and strain bursts.
• Traditional understanding links this behavior to size limitations and dislocation movement dynamics.

Purpose of the Study:

• To investigate an alternative mechanism for crackling noise in nano-pillars.
• To demonstrate how tailored precipitates can alter dislocation behavior and enhance stability.
• To challenge the conventional size-dependent explanation for crackling noise in nano-pillars.

Main Methods:

• Fabrication and characterization of Ti-based nano-pillars with tailored precipitates (300 nm to 2 μm diameter).
• Experimental analysis of crackling noise and stress drop distributions under compression.
• Microstructural analysis of precipitate behavior (ω-phase inclusions) under stress.

Main Results:

• Ti-based nano-pillars with non-rotatable precipitates showed classic power-law crackling noise (P(s) ∼ s⁻²).
• Tailored precipitates, acting as 'rotors,' shifted the stress drop distribution from power-law to exponential (P(s) ∼ exp(-s/s₀)).
• Rotors (ω-phase inclusions) align with slip planes, limiting dislocation glide and reducing stress amplitudes.

Conclusions:

• Precipitate-induced dislocation regulation provides a size-independent mechanism to control nano-pillar plasticity.
• The 'rotor' effect significantly weakens stress drops, enhancing material stability.
• This approach offers novel strategies for designing more robust and stable nano-pillars.