Abstract
Microstructural changes in grade 2 titanium generated by surface mechanical attrition treatment (SMAT) were studied using positron annihilation lifetime spectroscopy and complementary methods. A significant increase in the mean positron lifetime indicated many lattice defects introduced by SMAT. Two positron lifetime components were resolved in the positron lifetime spectra measured. The longer lifetime revealed the presence of vacancy clusters containing about 3 or 4 vacancies, while the shorter one was attributed to the annihilation of positrons trapped at dislocations. The changes of the positron lifetime indicated a decreasing dislocation density and the presence of a deeper layer with a higher concentration of vacancy clusters at the distance from the treated surface for which the microhardness approached the value for the strain-free matrix. Electrochemical impedance spectroscopy showed the positive effect of SMAT on the corrosion resistance of the titanium studied in a saline environment also after removal of the original oxide layer that was formed during the SMAT.
Highlights
There is a growing interest in nanocrystalline (NC) materials [1], or gradient materials with greatly refined structures of a subsurface layer
It is equal to 1.65 μm and 3.07 μm for surface mechanical attrition treatment (SMAT)-1 and -2 specimens, respectively, while the roughness of the reference sample without treatment was close to 1 μm
The increase of the surface roughness is in agreement with the results reported by Zhu et al who studied the influence of process parameters of ultrasonic shot peening on surface roughness and hardness of cp titanium [43,44]
Summary
There is a growing interest in nanocrystalline (NC) materials [1], or gradient materials with greatly refined structures of a subsurface layer. Methods based on severe plastic deformation (SPD) have become popular presently due to their simplicity and ease of applicability for plentiful classes of materials [2]. The application of these methods results in the creation of ultrafine-grained structure, as well as a great number of crystal lattice defects which introduction greatly changes the properties of the material. NC materials can be obtained only by methods that are based on non-homogeneous deformation with large strain gradients [3]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
