Browsing by Keyword "Titanium alloy"
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Item Creep failure mechanisms of a Ti-6Al-4V thick plate(2001-11) Seco, F. J.; Irisarri, A. M.; Tecnalia Research & InnovationThe creep failure operating mechanisms of a 17-mm thick plate of a Ti-6Al-4V alloy in various heat treating conditions have been investigated. Specimens in the as-received, mill-annealed, condition (50 min maintenance at 720°C and air cooled as the final step of the thermomechanical process) showed the lowest creep resistance and their metallographic analysis revealed that the temperature-activated dislocation climb was the mechanism responsible for the failure and that observed holes were generated by plastic deformation, rather than by creep cavitation. Conversely, maximum times to failure were recorded in beta-annealed specimens (1030°C for 30 min, air cooled and aged for 2 h at 730°C). The fracture surfaces of these broken specimens exhibited an intergranular morphology that was attributed to grain boundary sliding along the former beta grains. Finally, alpha-beta field-annealed samples (940°C 4 h, and furnace cooled at 700°C) possessed intermediate lives between those of mill-annealed and beta-annealed specimens and the failure operating mechanism was diffusional creep by the nucleation and coalescence of the creep cavities generated at the alpha-beta interfaces and the triple points.Item Influence of the filler metal on the mechanical properties of Ti-6Al-4V electron beam weldments(2010-07-23) Barreda, J. L.; Azpiroz, X.; Irisarri, A. M.; EXTREMAT; Tecnalia Research & InnovationThe influence of various filler metals on the mechanical properties of 17 mm thick Ti-6Al-4V electron beam welded joints has been analysed. Autogeneous welded joints exhibit higher toughness when compared to the parent plate but this improvement was less marked than that observed in plasma arc welded joints. To achieve better toughness, without suffering unacceptable losses of strength, different morphologies of commercially pure titanium filler metals have been employed. Using 0.50 mm thick sheet as filler metal leaded to maximum toughness but as counterpart a significant decrease in strength was observed. To obtain high toughness while maintaining a high strength level 0.25 mm sheet and 1 mm diameter filler metals are recommended. Fractographic examination of the failed specimens helped to explain the fracture behaviour of the different welded joints.Item X-ray photoelectron spectroscopy characterization of high dose carbon-implanted steel and titanium alloys(1999-04) Viviente, J. L.; García, A.; Alonso, F.; Braceras, I.; Oñate, J. I.; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOS; Centros PRE-FUSION TECNALIA - (FORMER); INGENIERÍA DE SUPERFICIES; Tecnalia Research & InnovationA study has been made of the depth dependence of the atomic fraction and chemical bonding states of AISI 440C martensitic stainless steel and Ti-6Al-4V alloy implanted with 75 keV C + at very high doses (above 10 18 ions cm -2 ), by means of X-ray photoelectron spectroscopy combined with an Ar + sputtering. A Gaussian-like carbon distribution was observed on both materials at the lowest implanted dose. More trapezoidal carbon depth-profiles were found with increasing implanted doses, and a pure carbon layer was observed only on the titanium alloy implanted at the highest dose. The implanted carbon was combined with both base metal and carbon itself to form metallic carbides and graphitic carbon. Furthermore, carbon-enriched carbides were also found by curve fitting the C 1s spectra. The titanium alloy showed a higher carbidic contribution than the steel implanted at the same C + doses. A critical carbon concentrations of about 33 at.% and 23 at.% were measured for the formation of C-C bonds in Ti-6Al-4V and steel samples, respectively. The carbon atoms were bound with metal to form carbidic compounds until these critical concentrations were reached; when this C concentration was exceeded the proportion of C-C bonds increased and resulted in the growth of carbonaceous layers.