In situ creep measurements on micropillar samples during heavy ion irradiation

We report on the development of an in situ micropillar compression apparatus capable of measuring creep under heavy ion beam irradiation. The apparatus has a force resolution of 1 μN and a displacement resolution of 1 nm. The experimental setup consists of a nanopositioner, a laser displacement sensor, and a microfabricated doubly clamped silicon-beam transducer. The system was tested by measuring the creep rate of amorphous Cu₅₆Ti ₃₈Ag₆ micropillars as a function of applied stress during room temperature irradiation with 2.1 MeV Ne⁺. Measured values of the irradiation induced fluidity are in the range 0.5-3 dpa^-1 GPa ^-1, and in good agreement with values obtained by stress relaxation experiments on other metallic glasses, and with predictions of molecular dynamics simulations. The in situ apparatus provides a practical approach for accelerated evaluation of irradiation induced creep in promising nuclear materials.