Easy glide

Of the 12 slip systems possessed by the CCP stmcture, five are independent, which satisfies the von Mises criterion. For this reason, and because of the multitude of active slip systems in polycrystalline CCP metals, they are the most ductile. Hexagonal close-packed metals contain just one close-packed layer, the (0 0 0 1) basal plane, and three distinct close-packed directions in this plane [I I 2 0], [2 I I 0], [I 2 I 0] as shown in Figure lO.Vh. Thus, there are only three easy glide primary slip systems in HCP metals, and only two of these are independent. Hence, HCP metals tend to have low... 

The constraint in polycrystals also removes the presence of the easy glide region observed in single crystals and, thus, work hardening immediately... 

Stage I Easy glide of dislocations with the possibility of large strains (-20%)... 

TEM observations of thin foils parallel to the primary (001) slip plane of the deformed samples show typical dislocation substructures for YCSZ in easy glide. The microstructure consists mostly of straight-edge dislocations and a few dislocation loops, as may be seen in Fig. 4.57. By means of the line-intercept technique, the average dislocation density was estimated to about 10 m . ... 

Fig. 4.56 Serrated stress versus strain curves in a 24 mol% YzOs-ZrOz specimen, com nessed at an imposed strain-rate of = 1.6x10 s between 1310 and 1450 °C. All the tests are performed in easy glide conditions [21]. With kind permission of Elsevier...

AM 350 exhibited extended regions of what appeared to be easy glide at 76 and 195 K as did AISI 304 to a lesser degree, at 76°K. In these regions, the flow stress decreased with increased plastic strain. In the case of the AM 350 alloy the flow stress actually fell below the recorded room temperature values at corresponding increments of plastic strain. 

Easy glide" regions and flow stress behavior at low temperatures in AM 350 and AISI 304. 

Periclase, MgO, has the rock salt structure. It is rare in the Earth s crust but is thought to be a major component in the lower mantle in a solid solution with FeO (magnesiowiistite). As with NaCl, the easy glide plane at low temperature is the... 

The solution of the deformation problem of the Csl crystal was based on the analysis and choice of the seed crystal orientation to minimize dislocation glide over the easy gliding planes. The solution of this problem is not straightforward, yet, as shown experimentally, it is quite feasible. It was established that the most admissible crystal orientation under specific temperature conditions corresponded... 

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