Effect of surface high density twin microstructure induced by shot peening on the fatigue behavior of Ti-6Al-4V

A detailed analysis of the surface high density twin microstructure and fatigue resistance of the Ti-6Al-4V titanium alloy specimens treated with the different shot peening parameters was conducted, compared with the as-received samples. Experimental results revealed that a high-density twinned structure layer formed on the surface of the shot peened Ti-6Al-4V titanium alloy. The predominant twinning type was {10 1¯ 2} extension twins. The density of twins decreases with increasing depth from the surface, and this phenomenon has been proven to be related to the strain rate. A shot peening intensity of 0.3mmA and 200% coverage are suitable, yielding superior surface integrity. Furthermore, shot peening can improve the fatigue life of the Ti-6Al-4V titanium alloy. This enhancement stems from the synergistic effects of the high-density twinned structure, compressive residual stress, and surface work-hardening, which collectively inhibit surface fatigue crack initiation and shift the initiation region to the subsurface, also impeding crack propagation.