Influence of Grain Boundaries on Short Fatigue Crack Growth in “Polycrystalline CMSX-4”

Grain Boundaries in Polycrystalline Alumina

Short and Large Crack , Mixed - Mode Fatigue - Crack Growth Thresholds in Ti - 6 Al - 4 V

There are few experimental results to date describing the crack-propagation threshold behavior of short fatigue cracks under multiaxial loading conditions. To address this need, in the present study, the variation in mixed-mode, high-cycle fatigue-crack growth thresholds with crack size and shape are reported for a Ti-6Al-4V turbine blade alloy, heat treated to two widely different microstructu...

The role of grain boundaries on fatigue crack initiation – An energy approach

In this paper, we construct a model for prediction of fatigue crack initiation based on the material’s microstructure. In order to do so, the energy of a persistent slip band (PSB) is monitored and an energy balance approach is taken, in which cracks initiate and the material fails due to stress concentration from a PSB (with respect to dislocation motion). These PSBs are able to traverse low-a...

Crack-Size Effects on Cyclic and Monotonic Crack Growth in Polycrystalline Alumina: Quantification of the Role of Grain Bridging

The role of grain bridging in affecting the initial rising portion of the R-curve and the transient, non-steady-state behavior of short cracks during (cyclic) fatigue-crack propagation has been quantitatively examined in a 99.5% pure alumina. Fatigue-crack growth properties for both long and short ( af < 2 mm) cracks emanating from machined notches (root radius, 15–150 m) were investigated, whe...

Tem Investigation of Grain Boundaries in Polycrystalline Silicon

The structure of two near-coincidence boundaries (close to a I = 7 and a Z = 9 misorientation) occurring in commercial poly-silicon has been examined in TEM. Both the structure of secondary dislocation networks as well as the occurrence of a-fringes (indicating a relative translation of the crystals along the boundary) were investigated. The near Z = 7 boundary is found to contain a simple netw...