通过引入梯度结构可以提升双相不锈钢的力学性能,然而其高度异质性结构会导致更为复杂多变的应力应变分配行为。为了深入研究梯度结构对双相不锈钢变形行为的影响,通过超声表面滚压处理(ultrasonic surface rolling processing,USRP)技...通过引入梯度结构可以提升双相不锈钢的力学性能,然而其高度异质性结构会导致更为复杂多变的应力应变分配行为。为了深入研究梯度结构对双相不锈钢变形行为的影响,通过超声表面滚压处理(ultrasonic surface rolling processing,USRP)技术制备了具有梯度结构的双相不锈钢,并采用晶体塑性有限元方法研究梯度结构中奥氏体和铁素体相的应力分配及相间协调变形机制。研究结果表明,经过USRP后材料表层的晶粒显著细化,且小角度晶界比例增加,铁素体晶粒中形成位错壁和位错胞结构,而奥氏体晶粒中形成层错和孪晶。另外,双相梯度结构中显著的异质变形诱导(heterogeneous deformation-induced,HDI)硬化效应,使试样屈服强度由581.34 MPa提升至690.98 MPa,表现出良好的强塑性组合。模拟结果显示,梯度双相结构中的相界和晶界处产生较大的应力集中,而细晶区的HDI硬化效应有效降低了铁素体与奥氏体之间的应变失配,缓解了局部应力集中。此外,在相同晶粒尺寸条件下,奥氏体与铁素体也会表现出不同的变形序列特征。在拉伸变形过程中,晶粒尺寸越小的区域微观异质性越低,高密度几何必须位错逐渐从表层向芯部扩展,使微观结构的异质性逐渐降低。揭示了梯度双相不锈钢在变形过程中的应变协同演化机制,为优化双相不锈钢的材料设计及综合性能提供了理论依据和试验支持。展开更多
The dynamic corrosion behaviors of Ti-6Al-4V alloy in acid artificial saliva containing fluoride ion were traced using electrochemical techniques,optical microscope,scanning electron microscopy,energy dispersive spect...The dynamic corrosion behaviors of Ti-6Al-4V alloy in acid artificial saliva containing fluoride ion were traced using electrochemical techniques,optical microscope,scanning electron microscopy,energy dispersive spectrometer and roughness tester.The experimental results indicate that a negative shift of corrosion potential as well as a continuous decrease in impedance for the alloy exists with increasing immersion time,and the degradation rate of the alloy presents the trend of first increase then decrease following the dissolution of passivation film and the formation of corrosion products.The accumulated fluoride ion on the alloy surface accelerates the fracture of passivation film,and the occurrence and development of corrosion of alloy are mainly located at the sites where the formation and shedding of white particles are composed of fluoride compounds,resulting in the decrease of corrosion resisting property of the alloy.A possible model is proposed to elaborate the dynamic corrosion behavior of the alloy.展开更多
基金Funded by the National Natural Science Foundation of China(No.50801057)the Engineering Research Center of Nano-Geo Materials of Ministry of Education,China University of Geosciences(No.NGM2018KF015)。
文摘The dynamic corrosion behaviors of Ti-6Al-4V alloy in acid artificial saliva containing fluoride ion were traced using electrochemical techniques,optical microscope,scanning electron microscopy,energy dispersive spectrometer and roughness tester.The experimental results indicate that a negative shift of corrosion potential as well as a continuous decrease in impedance for the alloy exists with increasing immersion time,and the degradation rate of the alloy presents the trend of first increase then decrease following the dissolution of passivation film and the formation of corrosion products.The accumulated fluoride ion on the alloy surface accelerates the fracture of passivation film,and the occurrence and development of corrosion of alloy are mainly located at the sites where the formation and shedding of white particles are composed of fluoride compounds,resulting in the decrease of corrosion resisting property of the alloy.A possible model is proposed to elaborate the dynamic corrosion behavior of the alloy.
