Lattice expansion of Ti–6Al–4V by nitrogen and oxygen absorption

Abstract

The effects of nitrogen and oxygen absorption on lattice expansion of Ti-6Al-4V have been investigated by high-temperature X-ray diffractometry. Experiments have been performed on stress-free powder for its high surface-volume ratio and to avoid possible effects on diffraction patterns due to texture change and recovery of defective structures induced by the measurement cycle at temperature. Cell parameters a and c, measured at increasing temperatures up to 600°C, show linear trends with different slopes. As temperature increases, the cell volume expands and the c/a ratio changes. This is due to both lattice thermal expansion and absorption of oxygen and nitrogen. Part of the gas remains entrapped in the metal after cooling to room temperature causing a residual lattice distortion. Results have been compared with literature data obtained in analogous tests performed on bulk Ti-6Al-4V alloy both in vacuum and in inert gas atmosphere.

Evaluating the effects of plasma diffusion processing and duplex diffusion/PVD-coating on the fatigue performance of Ti–6Al–4V alloy

“…Consequently, the less marked improvement in fatigue life (compared to the baseline annealed substrate condition) has to be explained by the difference in diffusion kinetics between oxygen and nitrogen under otherwise identical conditions. This can be attributed to two principal factors: (i) titanium is able to dissolve a larger quantity of oxygen than nitrogen ($31 at.% O vs. $10 at.% N at 700°C [41]) and therefore once the sample has cooled the resultant degree of supersaturation is less for the former; and (ii) lattice strain induced by oxygen located (mainly) in the octahedral sites of the hcp a-Ti structure is significantly lower for the same atomic content compared to nitrogen, both perpendicularly and along the basal planes [42]. As a result, less distortion is induced by oxygen located interstitially in the titanium lattice, and therefore lower levels of residual compressive stress are created.…”

Ductility Improvement Mechanism of Ti–6Al–4V+O Sintered Material

“…While the a-axis lattice constant increase was 0.7 © 10 ¹3 ¡, that of the c-axis was 4.0 © 10 ¹3 ¡. 7) XRD scanning was performed in the range of 2ª = 70°to 80°. The peaks around 2ª = 71.0°( Fig.…”

Effect of Indentation Size and Strain Rate on Nanomechanical Behavior of Ti-6Al-4VAlloy

“…Ti-6Al-4V is one of the most important and widely used Ti alloys in the aerospace industry especially for aero engine components, which are vulnerable to foreign object damage and solid particle erosion. Further, owing to its low density, excellent mechanical and corrosion resistant properties undue importance has been given in the scientific literature to the investigation of the mechanical behaviour of this alloy [15][16][17][18]. Few investigators have focused their research on the mechanical properties and deformation mechanism of this alloy at micro and macro scales using conventional indentation tests [19,20].…”