Effect Of Laser Shock Peening On Microstructure And Mechanical Properties Of TC11 Titanium Alloy

TC11 titanium alloy is mainly used to manufacture parts such as compressor disks,blades and drums of aero-engines,and can also be used to manufacture aircraft structural parts.Under actual working conditions,TC11 titanium alloys often have problems such as wear and fatigue break,and these failures begin at the surface.Therefore the wear resistance and fatigue resistance of blades is mainly improved by changing the surface stress state.Laser shock peening(LSP)can form a certain depth of residual compressive stress layer on the surface of the material,which can inhibit the initiation and expansion of cracks on the surface of the material and prolong the service life of the material.In this thesis,TC11 titanium alloy was subjected to laser shock peening under different conditions,and the effects of laser shock peening on the microstructure,hardness,residual stress,friction and wear performance and fatigue performance of TC11 titanium alloy were studied,and the optimal laser shock peening parameters were determined.The results show that micro-dents will appear on the surface of TC11 titanium alloy after laser shock.Such micro-dents increase or decrease with the change of laser energy,pulse width,bonding rate and absorbing layer material,and more micro-dents will increase the local roughness of the material.After laser shock peening,the local microphase will show a trend of refinement,and with the increase of laser energy,the surface residual compressive stress,surface hardness and section hardness will all increase,of which the maximum residual compressive stress is 416 MPa,and the depth is 780μm,and the maximum depth of the hardened layer is 1.5mm.After laser shock peening,the friction and wear properties of TC11 titanium alloy are improved.When the load is 15 N,the wear loss weight of the specimen without shock is 7.7mg,and the maximum wear loss weight after shock is reduced to 3.6mg.When the load is 35 N,its wear loss weight of the specimen without shock can be reduced to 8.3mg from the maximum value of 70 mg.The running-in time of the friction coefficient of the specimen without shock decreases from 400 s to 200 s.With the increase of laser energy,the average friction coefficient gradually decreases from 0.56 before shock to 0.25.At constant load,the wear scar depth gradually decreases with the increase of laser energy,but when the laser energy is the same,the wear scar depth increases with the increase of load.The main wear mechanism of the surface of TC11 titanium alloy without shock is adhesive wear,abrasive wear and delamination wear after wear,and the main wear mechanism is changed into abrasive wear after shock peening.The fatigue performance of TC11 titanium alloy is improved after laser shock peening.When the laser energy is 4J,6J and 8J,the rotary bending fatigue limit is increased by 22.4%,10.2% and 14.3%,respectively.After surface micro-polishing,the rotary bending fatigue limit under 6J energy is increased to 600 MPa,and the fatigue life under 4J and 8J has no obvious change after micro-polishing.After impact peening,the high-temperature endurance time of TC11 alloy is increased by 17.4%,and its life is increased with the increase of energy.After micro-polishing,the endurance time of the alloy under high temperature and low stress conditions does not increase significantly,but under low temperature and high stress conditions,the endurance time decreases.