| Titanium alloy is a commonly used metal material in marine and aerospace engineering applications,so it requires a good anti-corrosion and anti-hydrogen embrittlement properties.At present,surface modification method is often used to improve its surface mechanical properties.Laser peening(LP)is the use of impact effect in the alloy surface to introduce a certain residual stress to achieve surface modification of a new technology,which has better reinforcement effect,controllability and processing more flexible and so on.In this paper,TC4 titanium alloy was used as the research object to carry out the experiment of LP and electrolytic hydrogenation.By studying the microhardness,microstructure,tensile mechanical properties and macroscopic micro-fracture shape of TC4 titanium alloy before and after hydrogen charging.The effects of LP on the hydrogen embrittlement(HE)of TC4 titanium were discussed.The core research contents and achievements are as follows:(1)The mechanism of the laser shock wave on the surface of the alloy was analyzed from the theoretical point of view.The mechanism of the microstructure response of the TC4 titanium alloy during the strong plastic deformation was expounded.The LP path and the experimental parameters of LP on TC4 titanium alloy were developed.The diffusion behavior and its influencing factors were also revealed.The mechanism of anti-hydrogen embrittlement of LP was also discussed.(2)The microstructure and microhardness of the non-LPed and LPed TC4 titanium alloy before and after electrolysis were compared.According to the principle of LP,the influence of LP on hydrogen permeation was analyzed.The results show that the LP will introduce the residual compressive stress on the surface of TC4 titanium alloy,make the surface grains of TC4 titanium alloy refined,and the hydrogen concentration of the entering the sample during the hydrogenation process will vary with the decrease in grain size;hence,decreasing the HE susceptibility of the alloy.The hardness of the alloy after LP is improved,and the hydrogen-induced hardening occurs after the hydrogenation treatment.After the laser power densityincreases,the hydrogenation rate increases slowly and the LP impact becomes smaller its anti-HE properties.(3)The tensile properties of TC4 titanium alloy with and without LP were investigated by means of slow tensile test at room temperature before and after electrolysis.The results show that the tensile strength and elongation of the TC4 titanium alloy were improved by LP,and the tensile strength and elongation of the TC4 titanium alloy increased with the increase of the laser power density.After the electrolytic hydrogenation treatment,the tensile strength and the elongation decreased,and the decrease of hydrogen induced elongation decreased with the increase of laser power density,and the HE sensitivity of TC4 titanium alloy also decreased with the increase of laser power density.The fracture surface of the specimen was observed,and the microfractures were found to be typical dimple morphology.After the LP,the dimple was deeper,larger and uniform,showing better toughness.After electrolytic hydrogenation,the LPed TC4 titanium alloy was quasi-cleavable and the toughness was worse,but the TC4 titanium alloy after LP still exhibited good toughness. |
