Irradiation-induced strain localization and strain burst suppression investigated by microcompression and concurrent acoustic emission experiments

Plastic deformation of microsamples is characterised by large intermittent strain bursts caused by dislocation avalanches. Here we investigate how ion irradiation affects this phenomenon during single slip single crystal plasticity. To this end, in situ compression of Zn micropillars oriented for basal slip was carried out in a SEM. The unique experimental setup also allowed the concurrent recording of the acoustic emission (AE) signals emitted from the sample during deformation. It was shown that irradiation introduced a homogeneous distribution of basal dislocation loops that lead to hardening of the sample as well as strain softening due to dislocation channeling at larger strains. With the used deformation protocol strain burst sizes were found to be decreased due to channeling. The concurrently recorded AE events were correlated with the strain bursts and their analysis provided additional information of the details of collective dislocation dynamics. It was found that the rate of AE events decreased significantly upon irradiation, however, other statistical properties did not change. This was attributed to the appearance of a new type of plastic events dominated by short-range dislocation-obstacle interactions that cannot be detected by AE sensors.