Structural and phase changes under electropulse treatment of fatigue-loaded titanium alloy VT1-0

Abstract

The effect of electropulse treatment (EPT) of titanium alloy VT1-0 on the change of its fatigue life, structure and phase composition has been investigated. The study has shown that EPT improves the fatigue life by 1.3 times. Methods of TEM were used to analyze changes of the structure and phase composition of samples subjected to EPT and endurance testing. In the process of fatigue tests involving cantilever bending, a grain and sub-grain structure is formed in the surface of commercially pure titanium. The study has disclosed that the surface layer of the material has a multi-phase structure. Nano-crystal grains are formed by α-titanium. Oxide phase of titanium has been revealed, which is located along the crystallite boundaries of α-titanium. Particles of oxide phase have been identified exclusively in the top nano-structured layer. In the rest of the sample there are no particles of this phase. EPT causes dimensional changes of oxide phase particles and many-fold dimensional changes of crystallites in the surface layer. Owing to this treatment there are less internal stress concentrators in the surface layer of the material, which results, therefore, in cut down on probable spots of crack origination. Keywords: Titanium alloy, Electropulse treatment, Microstructure, Phase composition, Fatigue strength