Research On The Strengthening Mechanism And Comprehensive Performance Of TC11 Titanium With Gradient Nanostructure

Titanium alloy,a new structural material in the 20th century,is widely used in the manufacture of whole leaf plates,blades and fittings because of its high strength,high heat resistance and good corrosion resistance.Considering the fact of fatigue failure is the main failure mode of engine blade and gaining an adequate service life of engine blade,this paper mainly researched the fatigue fracture mechanism of the TC11 titanium alloy before and after ultrasonic impacting and rolling process(UIRP).The effect of UIRP on the basic properties of TC11 titanium alloy by analyzing their microstructure,hardness,S-N curve and fatigue fracture morphology also been researched.Based on the complex service environment and further study of UIRP effect on TC11 titanium alloy,the dry sliding friction and wear behaviors of TC11titanium alloy subjected to UIRP were studied to investigate the effect of UIRP on the wear resistance of TC11 titanium alloy.The study shows that the fatigue performance and wear resistance of TC11titanium alloy have a significant impact on the surface nano-enhancing caused by UIRP.Nanocrystals and residual compressive stress formed on the surface of the TC11 titanium alloy after UIRP.UIRP parameters included spindle speed of 240r/min,axial feeding rate of 10 mm/min,static force of 200 N and repeated processing 3 times.Research shows that fatigue strength corresponding to 5×10~6cycles of the TC11 titanium alloy was improved by 19.3%after UIRP.The results clearly show that the wear status of TC11 alloy after UIRP is better than that before UIRP under the same testing conditions.Analyzing the fatigue fracture mechanism based on the TC11 titanium alloy before and after UIRP:The crack source of TC11 titanium alloy before UIRP was on the surface of the sample,while the fatigue crack source regions all distinctly locate at near central positions and grow to failure under external cyclic loadings after UIRP.The fatigue fracture of the TC11 titanium alloy before and after UIRP all contain the typical three regions.Analyzing the friction and wear mechanism base on the TC11 titanium alloy before and after UIRP:For the untreated samples,the wear resistance first decreases and then increase with the sliding speed.Both the FC and wear rate reach a maximum value at 478 r/min,and the corresponding worn surface is the most serious.While for the UIRP samples,the trend is basically opposite,better results are obtained at 478 r/min.