微观组织对钛合金扩散连接层合板疲劳裂纹扩展行为的影响

Effect of microstructure on fatigue crack propagation behavior ofdiffusion-bonded titanium alloy laminates

采用扩散连接技术制备了TA2/TA2/TA2层合板。通过引入Ti55异质层制备了TA2/Ti55/TA2异质层合板。通过疲劳裂纹扩展试验,比较了两种层合板的疲劳寿命,研究了异质层对层合板疲劳裂纹扩展行为的影响。通过SEM和EBSD微观分析方法,揭示了异质层对层合板疲劳裂纹扩展行为的影响机理。异质层合板的疲劳裂纹扩展寿命是同质层合板的1.65倍。裂纹尖端从TA2层进入TA2/Ti55界面时,疲劳裂纹扩展速率降低了53.1%。界面壁垒增加、疲劳裂纹尖端塑性区尺寸减小和晶粒择优取向弱化均延缓了疲劳裂纹扩展速率的增速。

TA2/TA2/TA2 laminates were fabricated by diffusion bonding technology.Through introducing Ti55 heterogeneous layer,TA2/Ti55/TA2 heterogeneous laminates were fabricated.The fatigue life of two kinds of laminates was compared by fatigue crack propagation test,and the influence of heterogeneous layer on fatigue crack propagation behavior of laminates was studied.The influence mechanism of heterogeneous layer on fatigue crack propagation behavior of laminates was investigated by SEM and EBSD microscopic observations.The fatigue crack propagation life of heterogeneous laminate is 1.65 times of that of homogeneous laminate.Fatigue crack propagation rate decreases by 53.1%when the crack tip approaches TA2/Ti55 interface from TA2.The slow down of fatigue crack propagation rate results from the increase of interface obstacles,the decrease of plastic zone size of fatigue crack tip and lower preferred grain orientation.