Fig. 4
Preparation of ultrafine-grained nickel-titanium alloy root canal files. Reproduced with permission. Source: CNIPA, www.cnipa.gov.cn. a The preparation process of ultrafine-grained nickel-titanium alloy root canal files. b XRD graph. c DSC curves. d Microhardness plots of nickel-titanium, superfine-grained nickel-titanium, and superfine-grained nickel-titanium alloys after heat treatment at 400 °C. Figures 1, 2, and 3 indicate the microhardness plots of nickel-titanium alloy and ultrafine-grain nickel-titanium alloy, and 3 indicates the microhardness plots of ultrafine-grain nickel-titanium alloy after heat treatment at 400 °C. e Wear rate diagrams of nickel-titanium alloy, ultrafine-grain nickel-titanium alloy, and ultrafine product nickel-titanium alloy after heat treatment at 400 °C. Figures a and b indicate the wear rate graphs of nickel-titanium alloy and ultrafine-grain nickel-titanium alloy, and c indicates the wear rate graph of ultrafine-grain nickel-titanium alloy after heat treatment at 400 °C. f Electron micrographs of the prepared ultrafine-grain nickel-titanium alloy root canal files. g Wear surface morphology of nickel-titanium alloy. h Wear surface morphology of ultrafine-grain nickel-titanium alloy. i Wear surface morphology of ultrafine-grain nickel-titanium alloy after heat treatment at 400 °C