The ebct of hydrogenation-dehydrogenation on the microstructure of forping Ti-24Al14Nb-3V-0.5MO alloy was investigated by TEM and X-ray ddection. The resultsshowed that the microstructure consists of O and B2 phases a...The ebct of hydrogenation-dehydrogenation on the microstructure of forping Ti-24Al14Nb-3V-0.5MO alloy was investigated by TEM and X-ray ddection. The resultsshowed that the microstructure consists of O and B2 phases as received materials, and tmoprmation of B2 phase to O phase can be eNctively promoted 6y hydrogenation. The lamellate γ hydride was found in O phase with more hydmpen content, and this γ hydride could be decomposed by dehydmpenation treatment. The sole fine Ophase could be obtained 6y hydmpenation-dehydmpenation treatment, and two possible mechanisms for the microstructure improvetnent have been discussed on the basis of experimental results.展开更多
The Proccss of gascous hydrogcn charging into a Ti_3Al- based alloy in the temperature range of 500-650℃isinvcstigatcd. The rcsnlls snoxvc that in rclatiollshil, between the average hydrogen concentration at constant...The Proccss of gascous hydrogcn charging into a Ti_3Al- based alloy in the temperature range of 500-650℃isinvcstigatcd. The rcsnlls snoxvc that in rclatiollshil, between the average hydrogen concentration at constant tempreature and charging time reveals a parabolie rate law Applying the theory of lattice constant tcnlpcralurc and hrgillg tin rcvcals a parabolic riltc laiv. Applyillg tbcthcoly oftatticc dillbsio to allalyzc the hydrogcll diethesioll they andthat cncrgy of hydrogcn diffusion is 90.40 kJ/mol. and the equilibrium hydrogen content in the alloy depends on the temperature of the gaseous hydrogen charging process展开更多
Both hydrogen induced cracking and overload crack initiated at same characteristic distance, r~*,within the plastic zone along the slip line when the plastic zone developed to a critical ex- tent.For the overload crac...Both hydrogen induced cracking and overload crack initiated at same characteristic distance, r~*,within the plastic zone along the slip line when the plastic zone developed to a critical ex- tent.For the overload crack. K_(IC)=αr~*^(1/2)[σ_F^((n+1)/2n)/σ_(ys)^((1-n)/2n)],σ_F=σ_0+g[2μbσ_(th)/π~2L(1-v)]^(1/2) For the hydrogen induced cracking: K_(IH)=αr~*^(1/2)[σ_F(H)^((n+1)/2n)/σ_(ys)(H)^((1-n)/2n)], σ_F(H)={σ_0(H)+g[2μbσ_(th)(H)/π~2L(1-v)]^(1/2)}/k Hydrogen pomoting the dislocation multiplication and motion would result in σ_0(H)<σ_0, k>1,Therefore,hydrogen promoting the cleavage fracture in titanum aluminide can be due to that hydrogen facilitates the local plastic deformation,which results in σ_F(H)<σ_F and then K_(IH)<K_(IC).展开更多
文摘The ebct of hydrogenation-dehydrogenation on the microstructure of forping Ti-24Al14Nb-3V-0.5MO alloy was investigated by TEM and X-ray ddection. The resultsshowed that the microstructure consists of O and B2 phases as received materials, and tmoprmation of B2 phase to O phase can be eNctively promoted 6y hydrogenation. The lamellate γ hydride was found in O phase with more hydmpen content, and this γ hydride could be decomposed by dehydmpenation treatment. The sole fine Ophase could be obtained 6y hydmpenation-dehydmpenation treatment, and two possible mechanisms for the microstructure improvetnent have been discussed on the basis of experimental results.
文摘The Proccss of gascous hydrogcn charging into a Ti_3Al- based alloy in the temperature range of 500-650℃isinvcstigatcd. The rcsnlls snoxvc that in rclatiollshil, between the average hydrogen concentration at constant tempreature and charging time reveals a parabolie rate law Applying the theory of lattice constant tcnlpcralurc and hrgillg tin rcvcals a parabolic riltc laiv. Applyillg tbcthcoly oftatticc dillbsio to allalyzc the hydrogcll diethesioll they andthat cncrgy of hydrogcn diffusion is 90.40 kJ/mol. and the equilibrium hydrogen content in the alloy depends on the temperature of the gaseous hydrogen charging process
文摘Both hydrogen induced cracking and overload crack initiated at same characteristic distance, r~*,within the plastic zone along the slip line when the plastic zone developed to a critical ex- tent.For the overload crack. K_(IC)=αr~*^(1/2)[σ_F^((n+1)/2n)/σ_(ys)^((1-n)/2n)],σ_F=σ_0+g[2μbσ_(th)/π~2L(1-v)]^(1/2) For the hydrogen induced cracking: K_(IH)=αr~*^(1/2)[σ_F(H)^((n+1)/2n)/σ_(ys)(H)^((1-n)/2n)], σ_F(H)={σ_0(H)+g[2μbσ_(th)(H)/π~2L(1-v)]^(1/2)}/k Hydrogen pomoting the dislocation multiplication and motion would result in σ_0(H)<σ_0, k>1,Therefore,hydrogen promoting the cleavage fracture in titanum aluminide can be due to that hydrogen facilitates the local plastic deformation,which results in σ_F(H)<σ_F and then K_(IH)<K_(IC).
