Hall–Petch and inverse Hall–Petch effects accompany the long-term use of backup roll material

Hardness test and microstructure observation revealed that both Hall–Petch and inverse Hall–Petch effects accompany the studied long-term use of backup roll material. The increase of hardness with the decrease of grain size induced by contact fatigue damage at the early stages of use of backup roll material is consistent with the Hall–Petch effect. However, the lower resistance capability to endure longer use and prevent initiation of cracks following the nanocrystalline formation after long-term use corresponds to the inverse Hall–Petch effect.