Application of the FIB Lift-Out Technique for the TEM of Cold Worked Fracture Surfaces

Abstract

The FIB lift-out (LO) technique has been applied to a sample that been pulled to failure by tensile testing. An aluminum alloy (5083) was cold deformed using DSI's Maxistrain technology [1]. The alloy was cut with a low speed diamond coated wafering blade such that the fracture surface would fit inside the focused ion beam (FIB) specimen chamber. The sample was then mounted and placed in an FEI 200TEM FIB instrument. An FIB image of the tip of the fracture surface is shown in figure 1. A region for TEM specimen preparation was chosen such that the specimen would be in the plane of the tensile axis. The area of interest was chosen to ensure that FIB undercutting of the specimen could be accomplished upon tilting inside the FIB, and to ensure that the micromanipulator needle would have access to the FIB prepared specimen. A region of interest was coated with Pt using the FIB. A TEM specimen was then prepared in the usual LO manner [2,3]. The location of the finished LO specimen is circled in figure 1. After FIB milling was completed, the sample was removed from the FIB and placed on a light optical microscope stage. The electron transparent membrane was removed from the deformed sample using a glass rod attached to a micromanipulator. While the successful LO was performed, it should be noted that the micromanipulation was non-trivial due to the rough fracture surface combined with the poor depth of field of the light optical microscope.