Dwell sensitive fatigue in a near alpha titanium alloy at ambient temperature

The effect of grain orientation on fracture morphology during high-cycle fatigue of Ti–6Al–4V

“…These grains have been found to crack near the basal plane, closed squares in Figure 4(b), and not along the pyramidal plane for which they are favourably oriented for slip. Speculation previously has suggested that such grains act as crack initiation sites under conditions of load redistribution and are a more common aspect of dwell-fatigue loading [5,7]. In such cases, grains with a c-axis misorientation within 10…”

“…Under conditions of dwell fatigue, initiation sites are generally observed to occur in grains whose c-axis is near parallel to the loading direction [5,7]. In such grains the basal slip system is not at its maximum critical resolved shear stress value, yet fractures are observed to be close to the basal pole.…”

Analysis of Subsurface Fatigue Crack Generation in Ti–Fe–O Alloy at Low Temperature

“…1,2) The subsurface fatigue crack initiation sites in near-α and α-β type titanium alloys commonly appear crystallographic transgranular facet or facets. [1][2][3][4][5][6][7][8] Mostly the facets formed on or near the {0001} basal plane regardless their inclination to the principal stress axis. Dislocation movement in α phase is restricted on the primary slip plane and fairly planar so that dislocation arrays on {01 1 0} < 11 2 0 > are piled-up in the vicinity of grain boundaries and a local stress concentration generates near α grain boundary.…”

Life Prediction of Gas Turbine Materials

“…24. It has been perceived that the faceted fracture of α grains is driven by dislocation pile-up (Bache et al, 1997). Wu & Au (2007) have treated the problem in terms of the kinetics of Zener-Stroh-Koehler crack formation.…”

“…Basically, this is the essence of "cold dwell" vs. "hot creep". Bache et al (1997) studied IMI834 and plotted the dwell fatigue life as function of dwell time and stress as shown in Figure 26 (a) and (b), respectively. The model, Eq.…”