The Effect of Temperature and Strain Rate on the Hardness of Al and Al-Based Foams as Measured by Nanoindentation

In this work, we have used a nanoindentation system inside a temperature chamber to investigate the time- and temperature-dependent deformation behavior of the cell walls in an Al-based foam. Constant indentation strain rates were used to study the deformation behavior between room temperature and 100 °C. The depth-sensing indentation experiments were significantly influenced by a very strong, nonlinear thermal drift. Nevertheless, it was possible to measure the hardness as a function of indentation depth by measuring dynamically the contact stiffness and assuming a constant indentation modulus for the tested material. In summary, it was found that the hardness of the Al foam is twice as high as of pure Al, and the hardness decreases with increasing temperature and decreasing strain rate, following a power-law dependence.