Fractographic and microstructural analysis of fatigue crack growth in a Ti-6A1-4V fan disc forging

The constant amplitude fatigue crack growth behaviour of a conventionally (alpha + s) solution treated and aged Ti-6A1-4V fan disc forging was examined by fractographlc and microstructural analysis. The crack growth process was complex with many Interrelated fracture features. A transition in the fatigue crack growth curve correlated with a change from structure-sensitive to continuum-mode crack growth, primarily in the transformed and aged s grains, and a decrease in fracture surface roughness. The transition was most probably caused by the cyclic plastic zone size becoming equal to and exceeding the average platelet packet size. The significance of such transitions for prediction of fatigue crack growth and service failure analysis is discussed. This report has been prepared as a contribution to the AGARD-coordinated programme on Engine Disc Materials (TX 114)

[1]  G. Yoder,et al.  Observations on microstructurally sensitive fatigue crack growth in a widmanstätten Ti-6Al-4V alloy , 1977 .

[2]  F. Froes,et al.  Effect of microstructure, strength, and oxygen content on fatigue crack growth rate of Ti-4.5AI-5.0Mo-1.5Cr (CORONA 5) , 1984 .

[3]  D. Meyn.  An analysis of frequency and amplitude effects on corrosion fatigue crack propagation in Ti-8Al-1Mo-1V , 1971 .

[4]  G. R. Yoder,et al.  Quantitative analysis of microstructural effects on fatigue crack growth in widmanstätten Ti-6A1-4V and Ti-8Al-1Mo-1V , 1979 .

[5]  R.J.H. Wanhill,et al.  Low stress intensity fatique crack growth in 2024-T3 and T351 , 1987 .

[6]  G. Yoder,et al.  50-Fold Difference in Region-II Fatigue Crack Propagation Resistance of Titanium Alloys: A Grain-Size Effect , 1979 .

[7]  J. Chesnutt,et al.  Comments on the electron fractography of α-titanium , 1977 .

[8]  A. Rosenfield,et al.  Plastic zones in Fe-3Si steel double-cantilever-beam specimens , 1971 .

[9]  E. E. Underwood,et al.  Fractals in fractography , 1985 .

[10]  D. Meyn,et al.  Microstructural origin of flutes and their use in distinguishing striationless fatigue cleavage from stress-corrosion cracking in titanium alloys , 1981 .

[11]  G. Yoder,et al.  A Critical Analysis of Grain-Size and Yield-Strength Dependence of Near-Threshold Fatigue-Crack Growth in Steels. , 1981 .

[12]  C. Ward-Close,et al.  The influence of grain orientation on the mode and rate of fatigue crack growth inα-titanium , 1980 .

[13]  Subra Suresh,et al.  Crack deflection: Implications for the growth of long and short fatigue cracks , 1983 .

[14]  G. Leverant,et al.  Correlations between fracture surface appearance and fracture mechanics parameters for stage II fatigue crack propagation in TÏ-6AI-4V , 1974 .

[15]  R. Hertzberg,et al.  On the cyclic behavior of cast and extruded aluminum alloys. Part B: Fractography , 1983 .

[16]  A. A. Ten Have.  Cold Turbistan; final definition of a standarized fatigue test loading sequence for tactical aircraft cold section engine discs , 1987 .

[17]  G. Yoder,et al.  Fatigue crack propagation resistance of beta-annealed Ti-6AI-4V alloys of differing interstitial oxygen contents , 1978 .

[18]  C. Sullivan,et al.  LOW-CYCLE FATIGUE CRACK INITIATION IN Ti--6Al--4V. , 1969 .

[19]  Subra Suresh,et al.  Fatigue crack deflection and fracture surface contact: Micromechanical models , 1985 .

[20]  R. Wanhill.  Environmental fatigue crack propagation in Ti-6Al-4V sheet , 1976 .

[21]  G. T. Hahn,et al.  Local yielding attending fatigue crack growth , 1972 .

[22]  D. Tromans,et al.  Stage I corrosion fatigue crack crystallography in austenitic stainless steel (316L) , 1988, Metallurgical and Materials Transactions A.

[23]  E. Hornbogen,et al.  Microstructure and fatigue crack growth in a ?-Fe-Ni-Al alloy , 1976 .