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The surface treatment of Ti80 alloy with different microstructures was performed by laser shock peening (LSP), and the effect of LSP on Ti80 alloy on microstructure and corrosion properties was investigated. After LSP, the surface grains of Ti80 alloy with different microstructures were all refined, microhardness was significantly increased, and compressive residual stress was generated, and both microhardness and compressive residual stress showed gradient change characteristics along the layer depth. The corrosion resistance of Ti80 alloy with different microstructures was improved in both 3.5% NaCl solution and 5MHCL solution after LSP. Before LSP, the corrosion resistance of lamellar microstructure was the best, followed by bimodal microstructure and the worst by equiaxial microstructure, while the corrosion resistance of equiaxial microstructure exceeded that of bimodal microstructure under the combined effect of volume fraction of β phase, thickness of α phase and compressive residual stress after LSP. • A large number of dislocation tangles and deformation twins were formed in LSPed Ti80 alloy. • LSP can effectively improve the corrosion resistance of Ti80 alloys. • Corrosion resistance of untreated Ti80 alloy: lamellar > bimodal > equiaxial • After LSP, corrosion resistance of Ti80 alloy: lamellar > equiaxial > bimodal [ABSTRACT FROM AUTHOR]

In this work, supersonic fine particle bombardment (SFPB) was applied to modify surface of TC11 alloy and its impacts on microstructure and fatigue properties were systematically studied. The modified surface owned a nanoscale grain structure and a compressive residual stress with an amplitude of −196 MPa. The depth of hardened layer was about 300 μm. Afterwards, high-cycle fatigue behavior of SFPB modified alloy at −30 °C, 25 °C and 150 °C was studied, and the fracture surface, microstructure evolution, residual stress relaxation and microhardness of Ti alloy were characterized. The results show that the fatigue strength of the alloy is significantly improved by SFPB, and the fatigue strength decreases with the testing temperature. The deformation-induced martensite appears in the subsurface structure of Ti alloy tested at 25 °C and 150 °C, and the amount of deformation-induced martensite increases with the fatigue loading temperature. The compressive residual stress field induced by SFPB is relaxed in different degrees during fatigue loading. The degree of residual stress relaxation is the lowest under fatigue loading at 150 °C due to low cycle life. Mechanisms leading to the microstructural evolution and mechanical property variations were also proposed. • Surface nanocrystallization of TC11 alloy can be induced by SFPB. • SFPB can improve the fatigue strength of the TC11 alloy at different temperatures. • Deformation-induced martensite appears in the subsurface layer at 25 °C and 150 °C, but not at −30 °C. • Relaxation degree of residual stress is the lowest after fatigue loading at 150 °C. [ABSTRACT FROM AUTHOR]

Supersonic fine particles bombarding (SFPB) technology opens a new territory for engineering materials towards improved performances. Owing to its merits and emerging applications, 300M steel (tensile strength ≥1800 MPa) was treated with SFPB to create surface gradient nanostructures. The time dependent SFPB process was implemented on various 300M steel surface to investigate the microstructural evolution and mechanical property. 300M steel surface grains were sufficiently refined down to nanometer scale under high energy SFPB. In the subsurface layer, acicular martensite was found to be bent and broken, resulting in the high-density dislocation. At the early stage of SFPB, the impact affected area of 300M steel surface was deepened with increasing SFPB time, and the grains were constantly refined, which further lead to higher strength and improved hardness. However, after longer treatments of more than 90 s, bombardment energy accumulated at 300M steel surface resulted in grain growths and deteriorations of hardness. In particular, the newly formed microcracks substantially reduced the tensile strength. After SFPB treatment, the dimple size of the 300M steel surface fracture decreased significantly, and a large area of cleavage plane appeared, showing typical characteristics of ductile-brittle mixed fracture. • Surface gradient nanostructures of 300M steel has been created by SFPB treatment. • Dislocation motion has been found the dominant nano-crystallization mechanism. • Appropriate SFPB time can improve the mechanical properties of 300 M steel. • Mixed ductile-brittle fracture morphology was observed for SFPB treated 300 M steel. [ABSTRACT FROM AUTHOR]