A combined microtensile testing and nanoindentation study of the mechanical behavior of nanocrystalline LIGA Ni–Fe

Abstract

Abstract In this work, we studied nanocrystalline LIGA Ni-2.6 at.% Fe and Ni-5.6 at.% Fe with an average grain size of 10 nm. Microtensile samples were produced by the LIGA process including direct current electrodeposition. Microstructures and mechanical properties were investigated in the as-deposited state as well as after annealing at different temperatures. Results from tensile testing were compared to nanoindentation experiments with a particular emphasis on the strain rate sensitivity of the alloys. The Ni – Fe alloys were confirmed to be suitable LIGA materials for applications that require high hardness combined with microstructural stability and low internal stresses. For both alloys with 10 nm grain size, tensile yield strength and corresponding hardness values of the order of 2 GPa and 6 GPa, respectively, were found. After annealing at moderate temperatures (200 °C), strength and hardness increased although some grain growth was observed.