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EBSD of the steady-state microstructures revealed strong grain refinement.
This is mainly due to the fact that such alloys contain a large number of additional elements, which may act in a complex way during hot deformation.
In particular, the behavior of solidsolution niobium atoms is questionable; in spite of their low bulk diffusion rate, Nb solutes are able to interact with grain boundaries and reduce considerably grain-boundary mobility.
This may be due to the stabilization of dislocation walls by niobium solutes (i.e., decrease of dynamic-recovery kinetics) and/or the decrease of grain-boundary mobility, because substructure is usually swept out by moving grain boundaries.
It may be attributed to the decrease of grain-boundary mobility because thermal twinning during deformation is associated with grain-boundary migration [5].

In Cu, the trend is similar to Al so that most of the hardness values lie on a constant level, but close examination reveals that the angular variation is less as the number of the revolution increases.
There are grains with irregular configurations of grain boundaries and many dislocation are visible with the grains.
The grain size is reduced to ~1.5 µm and there are few dislocations within grains.
Some grains are present where many dislocations are visible.
Inspection reveals that there are grains with a low density of dislocations as indicated by an arrow whereas some grains contain many dislocations.

On the other hand, the strength of the alloy increased with increasing the number of passes up to 2, above which it decreased.
It has been reported by some researchers [12,13] that bulk ultrafine-grained (UFG) materials having superior ductility as compared to conventional large grained materials have been produced using ECAE.
This ECAE route was adopted since previous studies showed that route-BC produced a uniform microstructure of equiaxed grains separated by high-angle grain boundaries more rapidly than other routes [13, 26].
The deformation structure has been converted, for the most part, into a microstructure with ultrafine grains having low-angle and high-angle grain boundaries, and the dislocation density is low inside many grains.
In addition, decreasing of grain size during ECAE processing results in an increase of the amount of grain boundaries, which led to improvement in strength values (grain boundary strengthening).

The numbers along the horizontal and vertical axis correspond with the position in microns.
The interface crack length for the left grain is only 0.5 µm, which is much smaller than the interface crack length for the right grain, viz. 6.0 µm.
(a) Two α-Zn grains with similar crystal orientation.
(b) Two α-Zn grains with different crystal orientation, as indicated.
Acknowledgements This research was carried out under project number MC7.00075A in the framework of the strategic research program of the Netherlands Institute for Metals Research (www.nimr.nl).

A number of Mg–Al based alloys such as AZ91D, AM60 and AM50 have been extensively used for manufacturing automotive components such as the, steering wheel[3,5],instrument panel[5], seat frame[5,8,9].
The number in brackets is wall thickness.
Fig.2a shows the typical microstructure of die-cast AZ91D ,which is mainly composed of α-Mg phase and the continuous network phase distributed along grain boundaries, the grain size is 67;with 1.0 wt. % RE added, some new irregular block-like phase emerged throughout grain boundaries beside α-Mg matrix and discontinuous network phase , while the grain size is 55;increasing RE to 2.0 wt. %, grains are coarsened ( 83) decorated with lots of new phases emerge in the form of irregular larger block-like within grain or distributed along grain boundaries, the number of phases seem to be decreased, due to it is very cleaner within grains, but nearly network phase nearly disappears. .
Fig.4 (a) shows SEM image of Mg,Al,Mn and Zn elements for die-cast AZ91D alloy, it is obvious that Mg element existed within the grain,Zn element uniformly distributes within the grain or grain boundaries, while grain boundary area contains almost all the Al element and Mn element usually appears in the form of particles.
%RE alloy, the average grain is about 55 μm and 83μm, respectively.

The initial sample is composed of austenite grains of an average size about 30 µm, and numerous thermal twins with straight and parallel sides are visible.
After HCPEB treatment, craters can be seen clearly at the surface, while the initial grains were subdivided by deformation twins.
The variation in colors indicates a broad spectrum of local orientation within given initial grains.
Besides, the fast cooling of surface melting layer can produce very fine grains.
As a result, the surface microstructure will become finer with increasing the number of HCPEB pulses.

This study aims to investigate the effect of temperature and the number of cycle spheroidizing on mechanical properties and microstructure.
In this study, we thus investigate the effect of temperature and the number of spheroidizing cycles in low-carbon steel on mechanical properties and microstructure.
The grain size is 7.9, 6.7, and 5.6μm.
It will have more grain boundaries that cause the grain to be more difficult to move.
It was because of acceleration in recrystallization and grain growth mechanism at the higher temperature, so grain size increased, and grain boundary decreased.

A number of literature is available dealing with the effect of RRA treatment on SCC behaviour of 7xxx series (7050, 7075, 7020 etc.) alloys [6,7].
The ageing curve displays that the peak hardness (HV10 202) is attained at about 24 h, and this is attributed to the precipitation of primarily large numbers of fine disc shaped η'(MgZn2) precipitates.
Fig. 4a shows the TEM micrograph of T6 temper, consist of a large numbers of fine η' precipitates (~5 nm) within the grains and the distribution of continuous η precipitates (~20 nm) along the grain boundary.
Fig. 4b, the TEM micrograph of the RRA temper, exhibits also fine η' precipitates (~5 nm) within the grains and the η precipitates along the grain boundary.
Fig. 7a shows a number of pits (acted as stress concentration), cracks as well that have been initiated from the base of the pits and the propagation of cracks.

The results show that the alloy has the grain size of 42mm, straight of grain boundaries, intragranular no significant defects after solution heat treatment at 1063K. 
Figure 1 (a) is for the specimen with solid solution state, showing polygon equiaxial grains with average grain size of about 42 um measured by transversal-line method.
Irregular shape, fine grains with average grain degree of 1 um have the deformation flow lines (shown in arrow shown) in grains, which can be seen in Figure 1 (b) for specimen with the rolling deformation of 92%.
The intensity of {hkl} diffraction line is different for specimens with texture or without texture and intensity difference reflects the number of diffraction planes parallel to sample surface. 
Grain size of sample with solid solution state is 42um, the grain boundary is straight, no obvious defects are in crystal. 2.

Magnetic domain morphology showed that the number of domains increased after heat treatment, the exchange energy  between magnetic domains and the energy of magnetocrystalline anisotropy increased with increasing domain number,thus leading to better coercivity.
The domain orientation increases and the number of domains increases, the exchange energy  between magnetic domains and the energy of magnetocrystalline anisotropy increase.
On the other hand, there are plenty of precipitated phases impeding the movement of domain walls within grains or on the grain boundary [11].
(3) Magnetic stripe was very fuzzy,domain distribution was in confusion and magnetic anisotropy was weak before heat treatment.After heat treatment,The domain orientation enhanced and the number of domains increased,the exchange energy  between magnetic domains and the energy of magnetocrystalline anisotropy increased, meanwhile there were plent of precipitated phases within grains and on the grain boundaries,all the results maked the coercivity better, hysteresis losses higher and ratio of the remanence to saturation magnetization lager.
Temperature dependent mechanical properties of ultra-fine grained FeCo–2V.