Characteristics of a multicomponent Nb-Ti-Al alloy via industrial-scale practice

Within the spectrum of advanced intermetallic materials, an alloy containing 44Nb-35Ti-6Al-5Cr-8V-1W-0.5Mo-0.3Hf (at. %) was investigated in the industrial-scale produced condition. The alloy was tensile tested in air from room temperature to 1,000 C and in vacuum at 750 and 850 C. Results of this study have shown that the alloy can be commercially produced and has adequate ductility for its secondary processing even at an oxygen level of 1,160 wppm. The alloy has room temperature ductility of 16% and superplastic elongation of 244% at 1,000 C. This alloy shows low intermediate temperature (600--850 C) ductility when tested in air. The vacuum testing revealed that the low ductility is associated within oxygen embrittlement phenomenon. It is expected that such an embrittlement can be taken care of by an oxidation resistant coating. The alloy also possesses superior strength to similar alloys in this class. Results of this investigation suggest a strong potential for consideration of this alloy to exceed the useful temperature range of nickel-base superalloys

Characteristics of a multicomponent Nb–Ti–Al alloy via industrial-scale practice

Within the spectrum of advanced intermetallic materials, an alloy containing 44Nb-35Ti-6Al-5Cr-8V-1W-0.5Mo-0.3Hf (at. %) was investigated in the industrial-scale produced condition. The alloy was tensile tested in air from room temperature to 1,000 C and in vacuum at 750 and 850 C. Results of this study have shown that the alloy can be commercially produced and has adequate ductility for its secondary processing even at an oxygen level of 1,160 wppm. The alloy has room temperature ductility of 16% and superplastic elongation of 244% at 1,000 C. This alloy shows low intermediate temperature (600--850 C) ductility when tested in air. The vacuum testing revealed that the low ductility is associated within oxygen embrittlement phenomenon. It is expected that such an embrittlement can be taken care of by an oxidation resistant coating. The alloy also possesses superior strength to similar alloys in this class. Results of this investigation suggest a strong potential for consideration of this alloy to exceed the useful temperature range of nickel-base superalloys

In Situ Observations of the Deformation Behavior and Fracture Mechanisms of Ti-45Al-2Nb-2Mn+0.8 vol pct TiB₂

The deformation and fracture mechanisms of a nearly lamellar Ti-45Al-2Nb-2Mn (at. pct) + 0.8 vol pct TiB₂ intermetallic, processed into an actual low-pressure turbine blade, were examined by means of in situ tensile and tensile-creep experiments performed inside a scanning electron microscope (SEM). Low elongation-to-failure and brittle fracture were observed at room temperature, while the larger elongations-to-failure at high temperature facilitated the observation of the onset and propagation of damage. It was found that the dominant damage mechanisms at high temperature depended on the applied stress level. Interlamellar cracking was observed only above 390 MPa, which suggests that there is a threshold below which this mechanism is inhibited. Failure during creep tests at 250 MPa was controlled by intercolony cracking. The in situ observations demonstrated that the colony boundaries are damage nucleation and propagation sites during tensile creep, and they seem to be the weakest link in the microstructure for the tertiary creep stage. Therefore, it is proposed that interlamellar areas are critical zones for fracture at higher stresses, whereas lower stress, high-temperature creep conditions lead to intercolony cracking and fracture.The authors are grateful to Industria de Turbo Propulsores, S.A. for supplying the intermetallic blades. Funding from the Spanish Ministry of Science and Innovation through projects MAT2009-14547-C02-01 and MAT2009-14547-C02-02 is acknowledged. The Madrid Regional Government supported this project partially through the ESTRUMAT grant P2009/MAT-1585. C.J.B. acknowledges the support from Grant SAB2009-0045 from the Spanish Ministry of Education for his sabbatical stage in Madrid.Publicad

Superconducting and Structural Properties of Nb/PdNi/Nb Trilayers

The superconducting and structural properties of S/F/S (Superconductor/Ferromagnet/Superconductor) heterostructures have been studied by means of microwave measurements (1–20 GHz) and x-ray absorption fine structure (XAFS) spectroscopy. Nb/PdNi/Nb trilayers have been studied as a function of F layer thickness. With respect to pure Nb, XAFS analysis shows that the heterostructures exhibit larger structural disorder in the S layers. Microwave measurements show evidence for a progressively weaker vortex pinning with increasing F thickness. However, no clear correlation is found with the local disorder in Nb: the weakest pinning is not in the most disordered trilayer. Therefore, the structural disorder in the superconducting material cannot explain on its own the changes in vortex pinning. We argue that the F layer acts on the superconducting state