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The impact of slip occurrence in materials determines the large displacement of a crystal structure. In a study conducted on nickel superalloys, the slip activity is measured on initially pre-strained specimens in different directions. The incidence of slip, crystal/grain orientation and microstructure can be analysed by obtaining high-resolution digital image correlation (HRDIC) and EBSD maps. The effect of change in slip paths in different directions of loading is studied in order to quantify which slip system is likely to be active and cause the failure of the specimen. The HRDIC data quantifies slip bands within single grains and the EBSD data quantifies lattice rotations associated with the slip activity due to microstructural constraint. The analysis revealed the slip activity in every grain of the deformed specimen and in conjunction with relative displacement ratio (RDR) analysis, the active slip systems can be identified and compared with theoretical analysis obtained via Schmid factor calculations.
AIMS AND OBJECTIVES
AIMS AND OBJECTIVES
Crystal plasticity and Slip activity
Crystal plasticity and Slip activity
Slip occurs due to the motion of dislocations. This is initiated by the amount of stress applied, as illustrated in Figure 8. Slip occurs only when shear stress acting in the slip direction on the slip plane reaches a critical value. This initiation of the slip in grains is given as a component of shear stress known as critical resolved shear stress and the component of shear stress is known as resolved shear stress. Slip occurs only when resolved shear stress value is greater than critical resolved shear stress.
Slip planes and the slip directions are given by the Schmid factor. Slip primarily occurs on grains with the highest Schmid factor value. The resolved shear stress on the slip plane parallel to the slip direction is given as,
The value of τR at which slip occurs is a constant, known as the critical resolved shear stress τC. This is defined as Schmid's Law.
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