Recent research efforts have focused on intermittency in crystal plasticity. For examples, mechanical testing on microcrystals detects sudden strain bursts, which demonstrates criticality among relatively large and rapid dislocation events or avalanches. However, the origin of the dislocation events is not clear. Here we report on the dislocation avalanches in the slowly-compressed nanopillars of high entropy alloy AlxCoCrFeNi (x=0.1) as visualized by simultaneous electron dislocation imaging and nanoscopic mechanical measurements. The observation of dislocations is correlated with the load and displacement. By detecting larger nanopillar slips and observing dislocation events that precedes before and after, we show that the dislocation avalanches arise from the build-up of high density dislocation waves on different slip planes, which act as the source of intermittent emittance of dislocation arrays and avalanches. By correlating the dislocation wave dynamics, we gain further insights into the avalanche triggering mechanism .
 The work is performed in collaborations with Li Shu, Peter Liaw, and Karin A Dahmen and supported by NSF DMR and DOE BES.