Taming intermittent plasticity at small scales

• Main Authors: Zhanga, Peng, Salman, Oguz Umut, Zhang, Jin-Yu, Liu, Gang, Weiss, Jérôme, Truskinovsky, Lev, Sun, Jun
• Format: Journal Article
• Language: English
• Published: 10-10-2016
• Subjects: Physics - Materials Science
• DOI: 10.48550/arxiv.1610.02897

The extreme miniaturization in modern technology calls for deeper insights
into the non-conventional, fluctuation dominated mechanics of materials at
micro- to nano-scales. Both experiments and simulations show that sub-micron
face-centered-cubic (FCC) crystals exhibit high yield strength, which is,
however, compromised by intermittent, power law distributed strain
fluctuations, typical of wild plasticity. At macro-scales, the same bulk
materials show mild plasticity characterized by bounded, uncorrelated
fluctuations. Both anomalous strength and intermittency appear therefore as
size effects. While the former is highly desirable, the latter is detrimental
because stochastic dislocation avalanches interfere with forming processes and
endanger structural stability. In this paper we show that defectiveness, which
is used in classical metallurgy to harden materials, can be used at sub-micron
scales to suppress intermittent fluctuations. We quantify the coexistence of
wild and mild fluctuations in compressed Al alloys micro-pillars, demonstrate
that the statistical nature of fluctuations is determined by sample size, and
propose quantitative strategies allowing one to temper plastic intermittency by
artificially tailored disorder. Our experimental results are rationalized using
a theoretical framework which quantifies the competition between external (size
related) and internal (disorder related) length scales.