Influence spécifique de l'oxygène sur quelques propriétés physiques, les caractéristiques mécaniques et la dynamique de déformation plastique du titane de haute pureté

Oxygen/nitrogen-assisted embrittlement of titanium alloys exposed at elevated temperature

“…A decrease of all the macroscopic tensile properties (YS, UTS and STF) was found with the pre-oxidation time. While the ductility loss is consistent with all the reported literature on oxygen embrittlement in Ti alloys [6,15], loss in tensile strengths (YS and UTS) differs from results found on studies working on Ti-alloys with various and homogeneous contents of oxygen (up to 3000ppm) [5][6][7][8][9]. A point to mention is that the increase in YS and UTS was generally reported for high purity alloys with relatively low mechanical strength and for which solid solution strengthening would be important, regardless of minor element additions within the metal.…”

“…Working with graded materials originated from oxidation and oxygen insertion is not trivial since the stress state within the ONADZ and the non-affected region are unknown. The origin of such stress-states could arise from the expansions of the lattice parameters as a function of the oxygen content, leading to a ONADZ in a compression state and a core in tension, if the remaining Ti-6Al-4V is strong enough not to relax the deformation [6,12]. In addition, the effect of oxygen on the thermal expansion of the ONADZ would also lead to additional strains after oxidation and cooling down to room temperature.…”

“…1. Increasing the magnitude of the critical resolved shear stress (CRSS) of prismatic, pyramidal and basal planes [5], the yield strength [5][6][7][8][9], the hardening exponent [5,6]; 2. Changing deformation modes from single prismatic slip to double prismatic slip or multiple slip [10]; 3.…”

“…Changing deformation modes from single prismatic slip to double prismatic slip or multiple slip [10]; 3. Reducing the activation volume and enhancing static and dynamic strain aging phenomena [6,7]; 4. Decreasing primary, secondary and tertiary creep rates [7,11]; 5.…”

“…Increasing the dynamic elastic modulus of oxidized [11]; 7. Increasing the lattice parameters and volume unit cell [6,12]; 8. Decreasing the ductility [6,14,15].…”