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A large number of materials have been processed by electron beam direct manufacturing, including steels, Ti and Al alloys [ 5 - 8 ].
In particular, the process has been successfully demonstrated on a number of complex geometry titanium components as a replacement for titanium forgings by Lockheed Martin.
Zone III is located between Zones II and IV, where the grain structures change progressively from columnar grains to equiaxed Nitrogen infiltration ones.
Fine precipitates in the size range from 100 to 200nm are seen both inside the equiaxed grains and along the grain boundaries in Zone IV, as shown in Figure. 3e.
In the re-solidified weld beads of Al 6061, the grain structure changes progressively from columnar grains at the fuse boundary to equiaxed grains at the centre.

The contribution of RE alloying on the SME improvement is presumably attributed to a reduced stacking fault energy, the refined grain size and the solid-solution strengthening of matrix.
The shape recovery rate (η) of the alloys, with 4% tensile prestrain, as the function of RE-content and the number of trainings is illustrated in Fig. 1.
However, ≥ 0.30 wt% RE-addition will deteriorate the SME due to the coarse RE-compound particles existed within grains and at grain boundaries as was observed by SEM/EDS.
On the other hand, RE atoms are chemically active, and they strongly tend to form compounds and, in the present case of low concentration, to segregate at defects and grain boundaries.
Since the ε phase forms by a stacking fault mechanism [12] and a thin plate contains only limited number of faults, it is reasonable to believe that the segregation of RE at faults exists too.

On the other hand, in the case of alloy to addition Sm, α-Mg matrix morphology was changed from dendritc to equiaxed grains because of suppression of grain growth by formation of homogeneous intermetallic compounds containing Sm at grain boundary and α-Mg matrix [3].
The colors in the microstructure indicate different crystallographic orientation of the grains.
It is noted that Sm addition on the Mg-Al-Ca alloys suppressed the grain growth in as-cast microstructure.
After hot extrusion, the average grain size of Mg-5Al-3Ca and Mg-5Al-3Ca alloys was 4.8µm and 3.8µm, respectively.
Fig. 3 (b) gives an averaged value of a number of homogeneous load-unload curves chosen from the 5 individual curves for each alloy.

The reason is that grinding filing thickness of unchanged form of grinding grains is so small that compress force of edge for grinding grains is obvious as feed rate of workpiece is smaller.
When grinding with high speed, the number of grind grains joining cutting at the unit time is increased.
As enhancing for number of thermal pulse, the effect of both grinding thermal stress and extruding coexist so that residual stress is not increased rapidly but stable
All grain sizes of wheel are 80/100.
The reason is that the hardness of silicon carbon wheel and aluminum oxide wheel is similar with that of Al2O3 ³c(MPa) Vs(m/s) Journal Title and Volume Number (to be inserted by the publisher) 483 workpiece, so that cutting effect of wheel grain is feeble.

The component of SiO2 endowed the oxide scale with flat and compact structure, fine and even grains, and few exfoliating.
The polymerization of boron around grain boundaries expelled or hampered the other atoms(gas or nonmetal atoms) to diffuse and gather.
As shown in Fig.2(a,b), the grain boundary carbides in alloy No.4 with 0.015wt.% boron decreased obviously compared with that of alloy No.1 without boron, and the frame also became discontinuous chains, even grains from strong skeleton carbides.
As shown in Fig.2(c), grain boundaries of alloy No.5 were occupied by carbides and secondary borides by analysis of SEM and EPMA.
So at high temperature the borides around grain boundaries were easy to be oxidated.

Expansion pressure occurred easily in the higher water content LCAs and micro-cracks formed initially in the weak grains.
Then micro-cracks enlarged and spread to the mortar as the number of freeze-thaw cycles increased.
The LCA grains used in the tests were 10-15 mm in size.
However, in the case of the 30% water content, the weight loss of LCA reached about 7% and many grains fractured.
Micro-cracks formed in the LCA, then enlarged and spread to the mortar as the number of freeze-thaw cycles increased.

Minuscular mineral grains and compact micro-structure make jade materials exquisite.
Conversely, large mineral grains and the loose micro-structure make jade materials more rougher.
Large mineral grains and the loose structure make jade rougher.
However, minuscular mineral grains and compact structure make jade more exquisite.
Minuscular mineral grains and compact micro-structure make jade materials exquisite.

Dynamic recrystallization of the deformed zone forms an ultrafine - grained structure.
Because of high hardness and coarse-grained structure, caused by cold rolling process, mentioned copper plates were annealed in furnace at the temperature of 700°C for 1 hour to reach a fine- grained structure with desirable hardenability.
The base metal microstructure consisted of large elongated grains with an average grain size of 75μm is shown in Fig. 2a.As shown in fig 2b, microstructure in the nugget zone (SZ) is completely different from that of the base material.
Using two different rotation speeds of 300 and 600 rpm grain size variation was observed.
The mechanism of grain coarsening in friction-stir welded AA5083 after heat treatment.

The nominal composition of the alloy is Al-0.10Si-0.10Fe-2.40Cu-2.30Mg-6.55Zn-0.03Ti-0.13Zr (numbers indicate wt.%).
It can be seen from Fig. 1 that microstructures of DC ingot are coarse dendritic grains and the microstructures of LFEC ingot are fine equiaxed grains.
The average grain size of DC ingot is about 200µm while the LFEC ingot is 80µm.
The concentrations evolution of Cu, Mg, and Zn inside crystal grains during homogenization were analyzed by EPMA.
Fig.6 Dependence of element content inside grains on homogenization time.

Experimental procedures Polarization test and EIS test AZ31B Mg alloy powder with fine grains were prepared by roll compaction process (RCP) 3) .
In this work, the number of cycles in the grain refining process from the powder feeder to the roll granular is 0, 10, 20 and 50.
Each fine-grained powder via roller compactor system is compacted at room temperature by 1000 kN hydraulic press.
Fig. 2 shows the influence of the number of pass cycles on Icorr.
Fig. 3 shows the influence of the number of the pass cycles on Ecorr.