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Preparation of TEM specimens containing stress corrosion cracks in austenitic alloys using FIB

The bulk of the trench machining was performed using a 20nA beam current at 30 keV in a direction normal to the original sample surface. The final stages of machining were performed using a current of ~lnA and 30 keV, alternately tilting the sample by ±1.2° from the normal until the membrane thickness is less than lOOnm. This minimises tapering in the membrane thickness profile (Schmidt, 1997). Final cleaning was performed using 5 keV ions. A typical sample imaged using secondary electrons in the FIB, before the final machining, is shown in Fig. 2. Fig. 3 shows the same sample imaged in the TEM.