Fatigue Crack Growth In Niobium Aluminide Intermetallics

Abstract

The results of a recent study of the fatigue crack growth in a new class of niobium aluminide (Nb3Al) intermetallics alloyed with various levels of Ti are presented. The alloys studied have the following nominal compositions (note that all compositions are quoted in atomic &): Nb-15Al-10Ti(10Ti alloy), Nb-15Al-25Ti(25Ti alloy), Nb-15Al-40Ti(40Ti alloy) and Nb-12.5A1–41Ti-1.5Mo(41Ti alloy). Fatigue crack growth behavior was studied at room-temperature in all the alloys. Fracture mechanisms were determined by inspection of SEM images of fracture surfaces. Faceted cleavage fracture modes were apparent on the lOTi and 25Ti alloys. The 40Ti and 41Ti alloys exhibited clear evidence of ductile dimpled fracture. The ductile 40Ti and 41Ti alloys are shown to have comparable or better fatigue crack growth resistance than mill annealed Ti-6A1–4V. The effects of crack orientation (relative to elongated grains) on the fatigue crack growth behavior of the 41Ti alloy are also discussed.

High temperature strength, fracture toughness and oxidation resistance of Nb–Si–Al–Ti multiphase alloys

“…It is concluded from these results that the (Nb ss 1 Nb 3 Al 1 Nb 5 Si 3 ) three-phase alloy is promising for high temperature structural applications. The addition of titanium to Nb-based composites has been found to improve fracture toughness and oxidation resistance [13,14]. Fig.…”

“…In this study, plane-strain fracture toughness, K IC , and oxidation resistance of this threephase alloy have been investigated to examine the further potential for very high temperature structural applications. It was reported that the addition of titanium in multiphase alloys in Nb±Cr [13] and Nb±Al [14] system, which consists of Nb ss and intermetallic compound, improves remarkably fracture toughness. Moreover, titanium was reported to improve oxidation resistance of refractory alloys Science and Technology of Advanced Materials 3 (2002) 145±156 1468-6996/02/$ -see front matter q 2002 Elsevier Science Ltd. All rights reserved.…”

Evidence of void nucleation and growth on planar slip bands in a Nb-Cr-Ti alloy

“…On the other hand, dimpled fracture also occurs in materials such as Ti [4] alloys, which exhibit planar slip behavior but do not normally contain hard particles. Dimpled fracture has also been reported for Nb-Cr-Ti, [5,6] Nb-Al-Ti, [7,8] and Nb-Si [9] solidsolution alloys. The Nb-Cr-Ti alloy was a bcc Nb solid solution that contained 13 at.…”

Finite-element method simulation of effects of microstructure, stress state, and interface strength on flow localization and constraint development in Nb/Cr2Nb in situ composites

“…Thus, for fracture high-temperature aerospace applications. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Examples of toughness considerations, it would be desirable to eliminate these in situ composites include Nb-Ti-Hf-Cr-Al-Si, [2][3][4][5] Nbor delay particle fracture in in situ composites containing Cr-Ti-Al, [9,10] Nb-Cr-Ti, [11][12][13][14][15][16] Nb-Al-Ti, [7,8] and Mo-Sihard particles. B [17,18,19] systems.…”