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Grain Boundary Induced Lateral Propagation of Intermetallic Phases in Nano-Grained Cu-Sn Thin Film Couples Yu.
Introduction In view of technical importance of nanomaterials in the design and fabrication of integrated circuits, a number of fundamental studies concerning reactive interdiffusion in thin metal films [1-5] have appeared in the literature during the last two decades.
The phase formation process begins at the GBs around each grain and then phase front moves towards the grain center.
The propagation rates were sensitive to the grain size in the films: the smaller the grain size, the higher the rates.
Sn concentrations at GB around the grain and inside the grain at the spreading phase front, depend on the grain size.

Dislocation models of noneqiulibrium GBs have been developed in a number of works.
Along x direction numbers of type 1 and type 2 GB were chosen in a way to obtain a period close to 15 nm and disclination dipole separation (arm) of about 8 nm.
Li, Energy of grain boundaries between cusp misorientations, Surf.
Vladimorov, Disclination-structural unit model of grain boundaries, Philos.
Baudelet, Microstructures and hardness of ultrafine-grained Ni3Al, Acta Metall.

The Effect of Texture on the Fatigue Properties of Ultrafine-Grained Interstitial-Free Steel Thomas Niendorf1,a,† , Thorsten Marten 1,b, Hans J.
Despite the relevance of fatigue properties for many applications, only a limited number of studies is available that report on the fatigue properties of these materials.
For bcc and hcp materials only a very limited number of reports is available [15-17].
The IF steel was deformed using route E, a hybrid route with a rotation order of 180°/90°/180° within four passes, with a total number of eight passes.
equiaxed grains with similar grain sizes) and the local texture.

A number of physically based models are combined in order to predict microstructure development during hot deformation.
The models are applied to a number of laboratory experiments made on 304 austenitic stainless steel and the model parameters are adjusted from those used for low alloyed steel mainly in order to obtain the right kinetics for the influence of solute drag on climb of dislocations and on grain growth.
Fig. 5 shows the results for the grain size.
As the temperatures before quenching also increases with increasing number of roll pairs the time for recrystallization and grain growth will increase as indicated by the ovals in Fig. 4 and Fig. 5.
Calculated grain sizes for the different tests.

The average grain size of the ultrafine-grained surface layers (UF) is less than 2 µm, whereas the intermediate region (M) is medium-grained.
The grains in ultrafine-grained layers are elongated to the rolling direction.
For the case of the medium-grained material (M), the grain is almost equiaxial.
The number of grain size in the gage volume is about 5.6x104.
The number of measured points was 121.

One can build up a very significant amount of plastic strain in the material by increasing the number of passes.
The development of ultra-fine-grained materials with fewer number passes would make ECAE commercially attractive.
It is suggested that, in this type of material it might be possible to get ultra-fine/nano-crystalline material during ECAE with relatively less number of passes.
Some grains less than 100 nm are indicated by arrows.
It is suggested that in material with non-shearable particles it might be possible to get ultra-fine/nano-crystalline material during ECAE with relatively less number of passes.

The most effective way to reduce the stress concentration at grain boundary during deformation should be grain refinement.
The grain size (nominal grain size) of austenite was measured by quadrature method [7].
Grain size control of Fe-25Cr-1!
The effect of grain refinement becomes more significant when the grain size is reduced below 50 microns.
Figure 10 Relation between area fraction of intergranular fracture surface and grain size in Fe-25Cr-1N alloys. 300 400 500 600 700 800 900104 105 106 107 108 Maximum stress, σmax / MPa Number of cycles to failure, Nf / cycles Fe-25Cr-5Mn-1N (as-solution-nitrided) Fe-25Cr-5Mn-1N (grain-refined) ASTM F2229 100µm (a) d≒260µm 100µm (b) d≒60µm 30µm (c) d≒20µm 100µm (a) d≒260µm 100µm100µm (a) d≒260µm (a) d≒260µm 100µm (b) d≒60µm 100µm100µm (b) d≒60µm (b) d≒60µm 30µm (c) d≒20µm 30µm30µm (c) d≒20µm (c) d≒20µm Figure 9 SEM images showing fracture surface of tensile-tested Fe-25Cr-1N alloy as-solution-nitrided at 1473K for 43.2ks (a), grain-refined by reversion at 1473K for 0.9ks (b) and 0.12ks (c) after isothermal heat treatment at 1173K for 0.3ks. 300 0 10 20 30 40 50 60 70 800 50 100 150 200 250 Area fraction of intergranular fracture surface, A /% Grain size, d /µm Grain-refined materials As-solution-nitrided material 300 0 10

Effect of Surface and Grain Boundary on the Reversion of Al-Zn Alloys Keiyu Nakagawa1, a *and Teruto Kanadani1, b 1Okayama University of Science, 1-1 Kita-ku Ridai-cho Okayama, 700-0005, Japan anakagawa@mech.ous.ac.jp, bkanadani@mech.ous.ac.jp Keywords: Al-Zn alloys, Aging, Reversion, Grain boundary, Surface, Vacancy, GP zone Abstract.
Age-hardening of an Al-Zn alloy after quenching develops inhomogeneously due to the effect of surface as a vacancy sink and grain boundary as an easy path.
Grains were coarsened by the strain-annealing method to about 5mm in diameter.
Fig.2 shows variation of the isochronal curves in hardness at 0.49N of load with the position of indentation in the grain.
At several stages of the isothermal annealing, dependence of hardness number on the load of indentation was measured.

Harmonic structure (HS) is a structure in which the ultrafine grain (UFG) structure (Shell) covers the coarse grain (CG) structure (Core) and the fine grains are interconnected in a network.
Grain Orientation Spread (GOS) analysis by EBSD was performed to evaluate the misorientation of the grains.
That is, a grain with a higher GOS value contains a large number of dislocations.
The GOS value is represented as follows; For a grain i, the GOS is GOSi=1J(i)jωij (1) Where J(i) is the number of pixels of the grain i and ωij the misorientation angle between the orientation of pixel j and the mean orientation of grain i [4].
Acknowledgement This work was supported by JSPS KAKENHI Grant Number JP18H05256 and 18H05455.

With the time going, testing results show that coarse-grained alloys with larger grain size have higher impedance values and smaller corrosion current densities, indicating a better corrosion resistance than fine-grained specimens.
As temperature rises, grain size increases accordingly.
Grain growth is a thermally activated process, and the grain boundary area is the main source of energy, thus the system will evolve to reduce grain boundary quality and followed by the increase of grain size[13, 14]. 1# specimen shows fine grain with apparent and abundant short rod-like and sheet-like δ phases pinning at the grain boundary (Fig. 1a).
As shown in Fig. 2b, 1# and 2# samples have thinner grain size but more positive OCP values, by contrast, 3# and 4# are coarse grained but less positive OCP values.
For 1# and 2# specimens, although they also have numerous grain boundaries, but it can be clearly seen that these boundaries are occupied by a large number of precipitated particles - the δ phase, which may block the diffusion and slow down the formation of passive films.