Fig. 2: Fatigue resistance of the surface-nanolaminated gradient Ti.

a, b Number of cycles to failure plotted against stress amplitude (a) and fatigue crack growth rate da dN^-1 as a function of the applied stress intensity range ΔK for surface-nanolaminated gradient Ti, in comparison to the homogeneous coarse-grained (CG) Ti and gradient equiaxed-grained (GEG) Ti (b). c Fatigue crack growth rate at a stress intensity range of ΔK = 5 MPa m^0.5 versus yield strength of pure Ti manufactured with different microstructures. The data include homogeneous CG and ultrafine grained (UFG) structures^{12,59,60,61,62,63} as well as the surface nanolaminated structure (this work) and UFG structure at the surface regions of GEG Ti (this work and ref. ⁶⁴.). The yield strength for the latter two microstructures was converted from the Vickers hardness value, with details shown in Supplementary Fig. 5. Source data are provided as a Source Data file.