The Role of Stacking Fault Energy on the Indentation Size Effect of FCC Pure Metals and Alloys

ABSTRACTWe investigated the effect of stacking fault free energy (SFE), on the magnitude of the indentation size effect (ISE) of several pure FCC metals using nanoindentation. The metals chosen were 99.999% Aluminum, 99.95% Nickel, 99.95% Silver, and 70/30 Copper Zinc (α-brass). Aluminum has a high SFE of about 200 mJ/ m2, whereas α -brass has a low SFE of less than 10 mJ/ m2. Nickel and Silver have intermediate SFE of about 128 mJ/ m2 and 22 mJ/m2 respectively. The SFE is an important interfacial characteristic and plays a significant role in the deformation of FCC metals due to its influence on dislocation movement and morphology. The SFE is a measure of the distance between partial dislocations and has a direct impact on the ability of dislocations to cross slip during plastic deformation. The lower the SFE the larger the separation between partial dislocations and thus cross slip and dynamic recovery are inhibited. The SFE impacts pure metals differently from alloys. It was discovered that the characteristic ISE behavior for the pure metals was different when compared to the α-brass which is an alloy. Several additional alloys were chosen for comparison including 7075 Aluminum and 70/30 Nickel Copper.