This study investigates the effects of shot peening intensity

shot medium (cast steel shot and ceramic shot)

and composite shot peening on the fatigue properties of high-strength and high-toughness β-titanium alloy. Characterization techniques

including scanning electron microscopy (SEM) and X-ray diffractometry (XRD)

were employed to analyze the influence of shot peening processes on the surface integrity and fatigue fracture behavior of target materials. Experimental results show that shot peening effectively modifies the machined surface profile of target materials. With the increase of shot peening intensity (up to 0.25 mmA)

surface roughness increases

yet no delamination or micro-crack defects are observed

indicating excellent plasticity toughness of the target materials. However

the surface of target materials is sensitive to coverage: Local delamination and wrinkling defects occur on the surface after composite shot peening with 400% coverage. Shot peening introduces a residual compressive stress layer approximately 280 μm in depth on the surface of target materials. The residual stress value generally increases with shot peening intensity

but stress relaxation occurs in the near-surface layer (50 μm thickness) when the intensity reaches 0.22 mmA. Shot peening significantly enhances fatigue performance: Under cast steel shot peening conditions

the fatigue life increases by 145.4 times compared to the as-received state

with individual specimens reaching 1×107 cycles. Ceramic shot peening demonstrates more pronounced fatigue improvement at the same intensity. For peening with a single-shot medium

crack initiation sites shift to the subsurface layer

whereas composite shot peening reduces the average fatigue life significantly

with some crack sources appearing on the surface

attributed to surface damage and residual stress relaxation. In conclusion

high-strength and high-toughness β-titanium alloy exhibits favorable shot peening performance

low sensitivity to shot peening intensity (resistant to delamination or microcrack)

but high sensitivity to shot peening coverage

making it unsuitable for composite or extended shot peening treatments.