Taming intermittent plasticity at small scales

The extreme miniaturization in modern technology calls for deeper insights into the non-conventional, fluctuation dominated mechanics of materials operating at microscale. For instance, both experiments and simulations show that sub-micron face-centered-cubic (FCC) crystals exhibit high yield strength accompanied by intermittent, power law distributed strain fluctuations. At macro-scales, the same bulk materials show 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 quantify the coexistence of correlated and uncorrelated fluctuations in compressed Al alloys micro-pillars, demonstrate that the partition between the two 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 that quantifies the competition between external (size related) and internal (disorder related) length scales.

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