Influence of cryogenic treatment prior to laser peening on mechanical properties and microstructural characteristics of TC6 titanium alloy

In this study, the mechanical properties and microstructural characteristics of TC6 titanium alloy subjected to Cryogenic Treatment (CT) prior to Laser Peening (LP) were experimentally investigated by means of x-ray diffraction (XRD) technology, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) observations. Surface micro-hardness and tensile tests were also carried out. Experimental results showed that in comparison to single CT or LP process, CT prior to LP can induce finer grain size and higher dislocation density. Meanwhile, CT prior to LP can provide better mechanical properties. The surface micro-hardness and tensile strength of the specimen subjected to LP after CT with 18 h achieved an increase with 28.11% and 28.71%, respectively, while its elongation only reduced by the extent of 4.19% compared with untreated sample. Meanwhile, in comparison to the process of single CT or LP, LP after CT with 18 h provided the maximum amplitude compressive residual stress and Full Width at Half Maximum (FWHM) values, the values reached to −633 MPa and 2.47°, respectively. Additionally, based on the experimental results, the microscopic strengthening mechanism of CT prior to LP on the mechanical properties of TC6 titanium alloy was analyzed in detail.