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The plastic deformation of a high entropy alloy Al0.5CoCrFeNi was investigated by instrumented nanoindentation over a broad range of strain rates at room temperature. Results show that the creep behaviour depends on the strain rate remarkably. In situ scanning images showed a significant pile up around the indents, demonstrating that a highly localised plastic deformation occurred in the process of nanoindentation. Under different strain rates, contact stiffness and elastic modulus basically remain unchanged. However, the hardness decreases as indentation depth increases due to indentation size effect. For the same maximum load, serrations became less prominent as the loading rate of indentation increased. Similar serrations have been observed in the current alloy upon quasi-static compression.

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Shock compression response of a Zr-based bulk metallic glass up to 110 GPa J. Appl. Phys. 108, 083537 (2010); 10.1063/1.3501044 Temperature-dependent shear band dynamics in a Zr-based bulk metallic glass Appl. Phys. Lett. 96, 061901 (2010); 10.1063/1.3309686Effect of high strain rates on peak stress in a Zr-based bulk metallic glass J. Appl. Phys.Instrumented nanoindentation tests were used to investigate the mechanical properties of Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 bulk metallic glass. The corresponding loading strain rates were ranged from 0.002 s À1 , 0.02 s À1 to 0.2 s À1 . Plastic flow of this material exhibited remarkable serrations at low strain rates and increasingly became weakening until disappearance with increasing indentation strain rate, implying strong rate sensitivity. A significant pile-up around the indents was observed through atomic force microscopy, which suggested a highly localized plastic deformation. Mechanism governing the deformation was tentatively discussed in terms of the increasing process of free volume with a negligible temperature rise under low strain rate, which well explained the declining trend of elastic modulus and hardness with an increase of indentation depth. V C 2014 AIP Publishing LLC. [http://dx.