Effect of gas pressure on microstructure and mechanical properties of TC11 titanium alloy during supersonic fine particle bombardment
(1. School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471023, China;
2. Provincial and Ministerial Co-construction Collaborative Innovation Center for Non-ferrous Metal New Materials and Advanced Processing Technology, Luoyang 471023, China;
3. State Key Laboratory of Laser Interaction with Matter, Northwest Institute of Nuclear Technology, Xi’an 710024, China;
4. Nano and Molecular Systems Research Unit, University of Oulu, FIN-90014, Finland)
2. Provincial and Ministerial Co-construction Collaborative Innovation Center for Non-ferrous Metal New Materials and Advanced Processing Technology, Luoyang 471023, China;
3. State Key Laboratory of Laser Interaction with Matter, Northwest Institute of Nuclear Technology, Xi’an 710024, China;
4. Nano and Molecular Systems Research Unit, University of Oulu, FIN-90014, Finland)
Abstract: The surface nanocrystallization of a Ti-6.5Al-3.5Mo-1.5Zr-0.3Si (TC11) titanium alloy with a lamellar microstructure was carried out by supersonic fine particle bombardment (SFPB). The effect of SFPB gas pressure on its surface integrity, microstructural evolution and mechanical properties was systematically investigated. The results showed that gradient nanostructures on the surface of the TC11 alloy were successfully created after SFPB with different gas pressures. The grain size of the surface’s lamellar microstructure was completely refined to the nanometer scale. And the grain size of nanocrystals decreased with the increase of gas pressure. Meanwhile, the subsurface retained initial lamellar microstructure morphology. Surface roughness was minimized after SFPB with a gas pressure of 1.0 MPa, while microcrack formed at a higher gas pressure of 1.5 MPa, resulting in a decrease of compressive residual stress. With the increase of SFPB gas pressure, the surface microhardness and the depth of hardened layer gradually increased, and yield strength and tensile strength was improved. Nevertheless, the elongation was not greatly changed. The fracture morphology changed from typical ductile fracture to quasi-cleavage and ductile mixed fracture.
Key words: supersonic fine particle bombardment; gas pressure; titanium alloy; lamellar microstructure; surface nanocrystallization; microstructure; mechanical properties