On room-temperature nanoindentation response of an Al–Li–Cu alloy

Al-Li-Cu alloys are the least dense aluminum series with large applications in aerospace industries where mass plays an important role in calculations. In these applications, ambient- and elevated- temperature creep phenomena are among main failure mechanisms that should be assessed in detail for a safe service. Instrumented nanoindentation approach is a semi-destructive technique that can be well adapted to assess rate-dependent plastic deformation behavior of Al-Li-Cu alloys at room and elevated temperature. In the present paper, therefore, dual stage, constant loading-rate followed by constant-load, pyramidal nanoindentation tests were performed on an Al-Li-Cu alloy to assess time-dependent deformation behavior at room temperature. To this end, indentation size effect, indentation stress/strain rate, dislocations’ activation energy and activation volume and their dependencies upon indenter displacement (indentation depth) were analyzed. The results were used to assess and understand possible transition mechanisms during a dual stage indentation scheme of an Al-Li-Cu alloy.