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This resulted in higher stresses and strains making grain boundary susceptible to IGSCC.
A number of TEM micrographs and selected area diffraction (SAD) patterns were recorded and analyzed.
Twins and shear bands are linear features which have been observed to terminate at the grain boundaries.
Since the bands terminate at the grain boundary preventing the transmission of strain to the adjacent grain, local stresses as well as strain are expected to increase at the grain boundary and the grain boundary also gets disrupted as shown in fig. 3.
Such increased localised stresses and strains at the grain boundary and more dislocations at grain boundaries are expected to make these regions the preferred path for crack growth in simulated BWR conditions water in the non-sensitized condition.

Ultrafine-grained materials obtained by various techniques of SPD demonstrate unusual mechanical behavior and a number of unique properties often not achievable in coarse-grained materials [4-6].
It was shown in a number of studies that grain boundaries as an element of structure playing a determinative role in such materials markedly differ from those in common polycrystals, and are referred to as “non-equilibrium” or deformation-modified boundaries [7-16].
Thus, in the hafnium bronze more uniform fragmentation of structure with increasing true strain is observed, contrary to the commercially pure copper, in which the average grain sizes increased and the microhardness decreased with the increasing number of revolutions because of the development of relaxation processes [19].
Plasticity and grain boundary diffusion at small grain sizes.
Mössbauer Spectroscopy of Grain Boundaries in Ultrafine-Grained Metal Materials.

This process also can efficiently refine the ferritic coarse grained microstructure to nano-scale grain structure with well-defined grain boundary.
Fig. 2 shows the tensile strength of groove pressed low carbon steel sheets versus annealing temperature at different CGP pass numbers.
Fig. 6b shows the microstructure of two CGP passes sheet after annealing at 400 °C that in which the grains with insignificant grain growth can be observed, yet no abnormal grain growth can be observed.
Consequently, in the grain growth process (which occurs at elevated temperatures of post-annealing), the kinetic of growth for grains with dissimilar sizes is different resulting in abnormal grain growth.
I.F. distributions with annealing temperature and CGP pass number.

A thin dilution zone with a thickness of 50 µm is observed at the interface, and consists of a few TiB and TiC and a large number of lamella grains in which a thin needle-shaped martensitic microstructure is exist.
There is a dilution zone with a thickness of 50 µm at the interface, and is composed of a large number of lamella phase growing perpendicular to the substrate.
The interface morphology in a high magnification is shown in Fig.4 (d). a few fine TiB and TiC are present in lamella grain boundaries, and a thin needle-shaped martensitic structure is formed within lamella grains.
Subsequently, a eutectic microstructure in which TiB and TiC are embedded is formed along lamella grain boundaries.
A thin dilution zone with a thickness of 50 µm is formed at the interface, and consists of a few TiB and TiC and a large number of lamella grains in which a thin needle-shaped microstructure is exist by a martensitic transformation. 2.

The alloyed steels displayed an increase in the number of grains containing shear bands and strengthening of the {111} component after warm rolling compared to an unmodified low carbon steel [7].
Discussion The recrystallisation process and the final recrystallisation texture depend on the stored energy and the number and configuration of dislocations present in the deformed material.
The stored energy level is sensitive to the number of interstitial atoms present in the plane.
The higher values of stored energy in the LC steel are related to the higher amount of carbon in solid solution and, in turn, to the lower number of grains containing shear bands.
As reported by Barnett [13], a small number of deformed grains containing shear bands promoted the formation of a weak {111} recrystallisation component in this steel since the γ fibre forms preferentially at shear band boundaries.

Sintered SiAlONs are of two types with different microstructural features [22, 25]: (1) β-sialon grains plus glass, (2) β sialon grains plus crystalline YAG.
As the grain boundary composition changes, the aspect ratios of β grains vary and grain coarsening also occurs as sintering time or temperature is increased.
Effects of Grain Boundary Glass on Properties.
Grain boundary chemistry affects interfacial bond strengths.
Other practical advantages of high toughness values (KIc = 7-10 MPa.m1/2) include resistance to machining damage and improved fatigue behavior, KIc increasing with the volume fraction of elongated grains and proportional to (grain size) 1/2, an effect due to "crack wake mechanisms", such as crack bridging, grain rotation and grain pullout.

TEM studies confirmed that the structure ‘directionality’ increases along the number of passes.
The microstructure and the texture evolutions in the deformed and the recrystallized states were mostly investigated by SEM/EBSD in a number of samples deformed up to 2, 6 and 10 passes.
The number of applied passes had a strong impact on the global deformation behaviour and on the intensity of grain refinement.
The size of new grains close to coarse SPP is only occasionally greater than the average grain size, and their shape is nearly equiaxed.
The large grains resulting from intense grain growth were observed mostly in places far from the coarse SPPs.

Due to the ultrafine grains (or domains or particles) and a high density of grain boundaries (or generally interfaces) in nanostructured materials, many properties and performance of the materials are expected to be significantly varied with respect to their coarse-grained counterparts.
Ductility of nanostructured metals is found to decrease at smaller grain sizes, even for those ductile metals in coarse-grained forms.
Electrical conductivity Electrical resistivity increases with a decreasing grain size for metals due to the large scattering of electrons at grain boundaries.
Beside the grain size effect, the resistivity is also sensitive to the microstrain of the nano-metals which is related to the grain boundary structure.
Chemical reactivity Chemical reactivity of nanostructured metals is considerably enhanced due to the large number of grain boundaries.

A zone of fine grains is located next to the columnar ones, and at an interface with the bronze matrix much coarser grains are seen.
The Nb3Sn grains in continuous diffusion layers get larger by a factor of 1.5 and the grain size scattering broadens (Fig. 3, Table 1).
As seen from Table 1, Ti does not result in grain refinement of superconducting layers, which we already observed in a number of previous studies [8,11,16].
Parameters of Nb3Sn grain size distribution No.
There is a zone of columnar grains adjacent to the residual Nb, a zone of fine equiaxed grains and some amount of coarser grains at an interface with the bronze matrix, which is typical of bronze-processed wires.

The different colors are assigned to different grain orientations.
The nearly identical color of two grains means that the misorientation between these two grains is small.
The average grain size of the HPT AA5182 alloy is about 79 nm.
(a) Area fraction distribution of the grain size; (b) Number fraction distribution of the misorientation angle.
Meanwhile, with the reduction of grain sizes, dislocations are no longer sustained within grain and, once generated, rapidly diffuse to the GB [13,24].