Microstructure evolution and mechanical properties of tempered 5140 alloy steel after proton irradiation at different temperatures.

: This article introduces the effect of tempered 5140 alloy steel commonly used in engineering on its structure and mechanical properties under the action of proton irradiation. In the present study, the irradiation energy of 160 keV is applied to experimentally investigate the proton irradiation with different cumulative fluences on the tempered 5140 alloy steel. The effect of the cumulative fluence of the proton irradiation on the microstructure evolution of tempered 5140 alloy steel is studied through transmission electron microscopy. Moreover, the morphology of the tensile fracture is analyzed by scanning electron microscope. The effect of the cumulative fluence of the proton irradiation on the nanomechanical properties of tempered 5140 alloy steel is investigated with a nanomechanical tester. It is found that the surface hardening effect formed by the proton irradiation damage causes the dislocation density in the structure near the tempered 5140 alloy steel surface layer and such effect increases as the proton irradiation cumulative fluence increases. The results obtained show that the yield and tensile strength of the tempered 5140 alloy steel increase slightly as the cumulative fluence of the proton irradiation increases. However, the corresponding elongation decreases. For a stable pressure load of the nanoindentation, the hardness of the nanoindentation of the tempered 5140 alloy steel increases as the proton irradiation fluence increases. However, the corresponding indentation depth decreases. Based on the obtained results, it is concluded that proton irradiation has no significant effect on the macro- and nanomechanical properties of the tempered 5140 alloy steel. This may be attributed to the low energy of the proton irradiation, and the resulting radiation damage only acts on the thin layer of the tempered 5140 alloy steel surface.