Experimental Study of the Influence of Shot Peening on the Microstructure and Properties of Surface Layer of a TC21 Titanium Alloy
The effects of shot peening on microstructure and properties of surface layer of a TC21 titanium alloy have been studied by transmission electron microscopy, electron back-scattered diffraction, X-ray diffraction and Nano-indentation. The results indicated that an elastic-plastic strengthening layer was formed on the surface of the TC21 alloy after the shot peening. During the deformation processing, the activated slip systems were found to be in <a>, <c> and <a/c> planes with high-density dislocations formed as networks in α phase. After the shot peening, the residual stress was found in the strengthening layer, which decreased from the surface to the interior, and the thickness of the surface layer was measured about 370 μm. The hardness by nano-indentation measurement increased two times as compared with the original material. After the shot peening, the fraction of the low-angle boundaries between 0-10º was estimated as 59.3% at the depth of 100 μm from surface. This surface layer microstructure improved resistance of deformation of the TC21 alloy, and therefore increased its fatigue strength.