Steady-state nanoindentation creep test on β-Sn: A modified constant contact pressure method

Constant contact pressure (CCP) nanoindentation method is an emerging approach to studying the creep properties of materials at the micrometer scale. However, in the literature, the possible loss of contact when applying the CCP method may not accommodate low contact pressures when testing materials at high homologous temperatures. Here, we improve the previous CCP method by changing its control strategy and achieve a steady-state CCP nanoindentation creep on an example material, β-Sn, without the loss of contact. Our results show the measured power law stress exponent on the < 001 >-oriented grain is 7.1–8.5. Nevertheless, our CCP method still suffers from the inevitable scattering of measured contact pressures and strain rates. In this study, we also find that the stress relaxation during 5-s unloading induces significant plastic strain, which affects materials’ creep thereafter.