In the present study,effect of pile up on the nano-indentation tests of ODS ferritic steel was investigated.Specimens of 16Cr-3.5Al ODS steel were irradiated with high-energy Ne ions with 6.17 MeV/u at 220 K to two doses at SFC-T1 of HIRFL.Hardening of the irradiated specimens was tested with the nano-indentation technique.Significant pile up was observed around the indentation imprints.A typical morphology of the pile up is shown in Fig.1.Because of the pile up,the hardness data provided directly by the nano-indenter tend to overestimate the real value.In the present work,a method obtaining hardness from the load-displacement curves was proposed.From the load-displacement curves,the ratio of the irreversible work to the total work done by the indenter for a complete loading-unloading circulation((Wtot????Wu)/Wtot)increases with the increase of the irradiation dose,while the ratio of hardness to elastic modulus(H=E)decreases with the increase of irradiation dose,shown as.
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