显微组织对TC4钛合金氢化物转变的影响

Effect of Microstructure on Hydride Transition of TC4 Titanium Alloy

摘要:

采用电化学充氢结合多尺度表征技术，研究了片层组织与双态组织TC4合金中氢的扩散行为。结果表明，电化学充氢后，2种组织样品扩散表面均呈现氢浓度的梯度分布，且氢化层厚度相近。片层组织样品扩散层表面氢化物体积分数更大，氢化物变体优先在α/β界面形核并以孪晶对形式向α晶内生长。而双态组织由于等轴α晶粒尺寸较大，氢化物无法充满整个α晶粒，不同氢化物变体在α/β界面附近交替形核长大。TEM分析结果表明，2种组织样品中氢化物形核皆呈现层错调控的多级结构转变机制。

Abstract:

The diffusion behavior of hydrogen in lamellar and bi-modal TC4 alloys was investigated through electrochemical hydrogenation combined with multi-scale characterization techniques. The results show that after electrochemical hydrogen charging, the diffusion surfaces of lamellar and bi-modal samples present a gradient distribution of hydrogen concentration, and the thickness of the hydrogen diffusion layer of two samples is similar. The volume fraction of hydride in the diffusion surface of the lamellar sample is larger, hydrides preferentially form at the α/β interface and grow in the form of twin pairs into the α phase. In the case of the bi-modal sample, due to the relatively large equiaxed α grain size, hydrides cannot fill the entire α grain. Different hydride variants alternate in nucleation and growth near the α/β interface. TEM analysis results indicate that the hydrogenation nucleation in both microstructure samples presents a multi-level structural transformation mechanism regulated by stacking faults.