Fractographic study of fatigue crack growth processes in a fully lamellar γ-tiAl alloy

Balsone, S. J.; Worth, B. D.; Larsen, J. M.; Jones, J. W.

doi:10.1016/0956-716x(95)00250-y

Cited by 30 publications

(10 citation statements)

References 6 publications

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“…Figure 4 shows the fatigue fracture surfaces of the nearly lamellar material tested in dry air. In the case of the R–C crack plane orientation, interlamellar or intralamellar 15 fracture paths were dominant [Fig. 4(a)] irrespective of the stress intensity factor range, whereas in the case of the L–C crack plane orientation, translamellar transgranular crack was dominant over the fracture surface [Fig.…”

Section: Resultsmentioning

confidence: 99%

Environmental fatigue crack growth in titanium aluminides and hydrogen evolution behaviour

Minoshima

Obara

Minamino

et al. 2001

Fatigue Fract Eng Mat Struct

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The influence of environment on fatigue crack growth behaviour was investigated both in nearly lamellar and in duplex titanium aluminides, and the hydrogen evolution kinetics was analysed by thermal desorption spectroscopy. The tensile strength of the duplex material decreases in the order of the extent of the water molecule content in the environment: the strength in vacuum is the highest, and decreases in the order of laboratory air and finally in water. In the case of the lamellar material, the fatigue crack growth rate in dry air is higher in the R–C crack plane orientation than that in the L–C crack plane orientation. The crack growth rate becomes higher when the crack grows as the lamellae tear. However, in the case of the duplex material, the crack growth rate in the R–C crack plane orientation is smaller in the low ΔK (ΔKeff ) region. When cathodic charging is applied, the fatigue crack growth rate becomes higher than in dry air, particularly in the higher stress intensity factor range. The hydrogen evolution rate is increased by cathodic charging, with lower temperature peaks and higher ones. The peaks at lower temperatures are correlated with the decomposition of hydrides and de‐training of hydrogen from microstructural imperfections such as microvoids. As‐received materials also show an evolution peak at a higher temperature, and the evolution rate is almost independent of cathodic charging. In addition, the evolution rate at a high temperature (above 800 °C) is increased by cathodic charging. The hydrogen is considered to have an important role on fatigue crack growth acceleration.

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Section: Resultsmentioning

confidence: 99%

Environmental fatigue crack growth in titanium aluminides and hydrogen evolution behaviour

Minoshima

Obara

Minamino

et al. 2001

Fatigue Fract Eng Mat Struct

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“…The effects of microstructure on strength and ductility, [1,2,22,23,[39][40][41][42]48] fracture toughness, large crack fatigue crack growth resistance, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][17][18][19] and creep resistance of cast and forged TiAl alloys [2,40,49,50] are well established. One of the least understood areas of TiAl alloys is the fatigue crack nucleation process [32] and the growth of small cracks [13,20,21] into large, fatal cracks.…”

Section: Introductionmentioning

confidence: 99%

Fundamental aspects of fatigue and fracture in a TiAl sheet alloy

Chan

Shih

1998

Metall Mater Trans A

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The fatigue mechanisms in a TiAl sheet alloy, heat treated to the lamellar and equiaxed microstructures, were studied to determine the effects of microstructure on the initiation of microcracks and their subsequent growth into large cracks. The nucleation and growth history of individual microcracks were followed. For comparison, fatigue crack growth and fracture toughness were also characterized using specimens containing a machined notch with a fatigue precrack. The results indicated that microcracks initiated at grain/colony boundaries and at slip bands. Most microcracks were arrested after nucleation, but a few grew at stress intensity ranges below the large crack threshold. The populations of nonpropagating and propagating cracks varied with life fractions. Ligaments in the wake of a fatigue crack were more severely strained than the crack-tip region of the main crack, and, as a result, they were more prone to fatigue failure. The destruction of the crack-wake ligaments is expected to result in lower fracture resistance in materials under cyclic loading than those under monotonic loading.

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“…[1,2,3] Improvements have taken place in alloy design, processing, phase relations, mechanical properties, and fundamental understanding of microstructure/property relationships. As a result, the effects of microstructure on the strength, [3,[6][7][8][9][10] fracture, [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] fatigue, [3,9,25,[27][28][29][30][31][32][33][34][35] and creep resistance [9,[36][37][38] in TiAl alloys have been studied extensively with the aims of understanding and further improving the damage tolerance properties. [4,5] Research on TiAl alloys has been motivated by the desire to improve the mechanical properties of TiAl alloys so that they can be used reliably in components that demand damage tolerance.…”

Section: Introductionmentioning

confidence: 99%

Fatigue and fracture behavior of a fine-grained lamellar TiAl alloy

Chan

Shih

1997

Metall Mater Trans A

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The fatigue and fracture resistance of a TiAl alloy, Ti-47Al-2Nb-2Cr, with 0.2 at. pct boron addition was studied by performing tensile, fracture toughness, and fatigue crack growth tests. The material was heat treated to exhibit a fine-grained, fully lamellar microstructure with approximately 150-m grain size and 1-m lamellae spacing. Conventional tensile tests were conducted as a function of temperature to define the brittle-to-ductile transition temperature (BDTT), while fracture and fatigue tests were performed at 25 ЊC and 815 ЊC. Fracture toughness tests were performed inside a scanning electron microscope (SEM) equipped with a high-temperature loading stage, as well as using ASTM standard techniques. Fatigue crack growth of large and small cracks was studied in air using conventional methods and by testing inside the SEM. Fatigue and fracture mechanisms in the finegrained, fully lamellar microstructure were identified and correlated with the corresponding properties. The results showed that the lamellar TiAl alloy exhibited moderate fracture toughness and fatigue crack growth resistance, despite low tensile ductility. The sources of ductility, fracture toughness, and fatigue resistance were identified and related to pertinent microstructural variables.

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Fractographic study of fatigue crack growth processes in a fully lamellar γ-tiAl alloy

Cited by 30 publications

References 6 publications

Environmental fatigue crack growth in titanium aluminides and hydrogen evolution behaviour

Environmental fatigue crack growth in titanium aluminides and hydrogen evolution behaviour

Fundamental aspects of fatigue and fracture in a TiAl sheet alloy

Fatigue and fracture behavior of a fine-grained lamellar TiAl alloy

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