Hydrogen Induced Delayed Fracture Behavior In Titanium

In this paper, the problems relevant to the hydrogen embrittlement of titanium alloy has been summarized comprehensively. And based on those vies, the influence of hydrogen on the microstructure and mechanical properties of the titanium alloy Ti-2Al-2.5Zr was studied, the solubility of hydrogen in the alloy has been measured, hydrogen induced delayed fracture behavior in it has been investigated, and finally the hydrogen induced delayed fracture behavior model was proposed.By analyzing the phase, we know the crystal lattice of Ti-2Al-2.5Zr with a phase being a =0.295nm, c=0.468nm. After being hydrogenated, TiH2 with fee structure will precipitate in the interface and a phase, the crystal lattice a = 0.444nm. TiH2 distribute in the a -matrix randomly and is black with pin shape, and the size of TiH2 with hydrogen increasing .By study the influence of hydrogen on specific heat of Ti-2Al-2.5Zr, the solubility equation of hydrogen in the alloy has been gotten : CH=16914exp (-1965.7/T) . At room temperature, it's solubility is 24 ?g/g.By sustained loading test, it is found there have hydrogen induced delayed fracture behavior in the samples as follows: with 110?g/g hydrogen at room temperature and 100?, with 250?g/g and 490?g/g at 100?. The crack propagation velocity vs. stress intensity factor curves has typical two-stages characteristics. In the stage I ,the crack does not split until K I >Kth , and crack growth velocity(da/dt)1 does not increase significantly with stress intensity factor K I. When K I >K I h, it comes to the stage II, (da/dt)II increases rapidly with K I increasing, and the specimen fractured when K I extend to critical value KC. The value of Kth, K I h, KC of samples contain different hydrogen at differentcircumstance as follows:With 110 u g/g hydrogen at room temperature: 45