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Fig. 1a shows the optical micrograph of the etched 304SS, which was coarse-grained, with a mean grain size of 100μm.
In addition, the Nano-304SS was nano-grained, the mean value of the grain size being 39 nm according to XRD determination using the Scherrer equation.
The Nano-304SS is composed of nanocrystalline grains, in which the grain boundary GB serves as a “short-circuit path” for diffusion.
Furthermore, a large number of GBs in the Nano-304SS may cause a reduction of the Cl− concentration at each GB with respect to the Cl− concentration at each GB in the coarse-grained 304SS, which also decreases the driving force for pitting initiation.
This ability is achieved by the grain refinement, which becomes from bulk grain size to nano grain size.

Aiming sample identifications, they were labeled in alphabetical order, A,B,C and D, followed by a number that indicates the total amount of the Y2O3 additive, as presented at table 1.
Electric behavior of sintered samples was evaluated with complex impedance spectroscopy technique, which allows to measure separately the grain resistivity and grain boundary resistivity.
The ionic conductivity (σ) of grain, grain boundary and total were calculated using reciprocal of equation (1).
In this case is possible to highlight the existence of two semicircles, assigned to grain resistivity for high frequencies and to grain boundaries for intermediate frequencies.
(A) (B) Figure 5 – Arrenhius graphics of grain (A) and grain boundary (B) conductivities in temperature range between 276 e 550°C for samples A-9%, B-8%, C-7%, D-6% and ZrO2:3%mol Y2O3 without additives. In figure 5 (A), relative to grain interior, it is observed that in temperatures around 550 0C the samples A-9% and B-8% have better conductivities.

Generally speaking, minute amount of RE elements can reinforce the hardness of stainless steel, because they can not only partial gather in grain boundary, promote to fine grain, but also form intermetallic compound with other elements, the second phase reinforced the steel.
According to the reference[7-8]: proper amount of rare earth elements can improve the size and shape of carbide and inclusion, purify and strengthen grain boundaries, fine grain size and fine precipitation phase size and inhibit the formation and extension of crack starter, to improve mechanical properties of the steel.
There are large number of white light-colored inclusions at the bottom of the dimples.
Because of the particle size and precipitation phase are increasing, the number and size of the dimples are increasing too, dimples become shallow, lead to toughness and strength of the materials are both sharply reduced.
Too much rare earth in steel can make the rare earth compounds separate out, at the grain boundary and in grain interior, it will form potential difference between the second phase and substrate metal, microbattery increase the corrosion rate of stainless steel.

Alloys available for conventional aluminium alloy production processing are well established and contain a vast number of alloy options which may be matched depending on application.
Wrought and cast aluminium alloys are designated by a four-digit numbering system developed by the Aluminium Association.
Results showed improvement in the mechanical properties and a greater number of equiaxed grains in the sample fabricated via the hybrid process compared to the sample fabricated via WAAM.
After T73 heat treatment, the grain boundary became less pronounced due to precipitates reapportioned uniformly from grain boundary into the grain structure and grain growth became restrained by TiC nanoparticle through grain boundary pinning.
With the heat treatment, the grain boundary became slightly defined due to precipitates being reallotted consistently from the grain boundary into the grain structure and grains increased due to growth being restrained by TiC nanoparticles because of the pinning effect on the grain boundary.

The inherently poor workability of magnesium alloys is due to the limited number of slip systems associated with the HCP crystal structure.
Most of the grains for both alloys are equiaxed; however, some grains are elongated in extrusion direction.
In addition, the grain size of alloyⅡis smaller than that of alloyⅠ.
The contour numbers represent power dissipation efficiency.
DRX grains are uniform but grow at high temperature and strain rate (673K, 10s-1, Fig.6f).

Fig. 3 The influence of ZrO2 and MnO2 make Fig. 6 The influence of ZrO2 and MnO2 make on bulk density and relative density on rockwell hardness of samples Fig. 4 The influence of ZrO2 makes on Fig. 5 The influence of MnO2 makes on rockwell hardness of samples rockwell hardness of samples And bulk density of 4%ZrO2-MnO22.0wt% was largest, it may be because the grain size distribution was more uniform, then the porosity reduced and density was improved.
As toughness of products increasing, grain boundary phase increased.
The possible reason is when length of the micro-cracks in the products and increasing of the numbers of micro-cracks , products has poor toughness, low hardness and poor wear resistance.
But when the ZrO2 content is more than 4%, polymorph transformation of ZrO2 may produce excessive micro-cracks, then grain boundary phase can not combined with grain and abrasion resistance induced.(2)From Fig. 8,we can know wear loss first increased and then decreased with the increasing of MnO2.The results may be MnO2 and Al2O3 formed a solid solution, then the binding force of the grain boundary increased.
In addition, the grain is not easy to be detached from the grain boundaries at the micro-cra cks and the wear resistance increased.(3)Figure 9 shows that when adding 4% ZrO2-2.0% MnO2, wear loss of samples was least.

TEM observations of the as-received materials proved that silica 3 Fig.1 Microstructure of MoSi2 (a) and MoSi +20% SiC(b) (SiO2) particles were frequently present in the triple grain junctions of MoSi2 grains and occasionally were placed intragranularly, inside the MoSi2 grains.
The strength degradation defects in the composites were mainly pores sized from 15 to 80 �m and clusters of SiC grains.
This fact is also supported by TEM observations of the samples after creep testing, where a large number of dislocations in the MoSi2 grains has been found, Fig. 6.
In the materials studied in the present investigation the grain size of the MoSi2 in MoSi2 + SiC composite is significantly higher in comparison with the grain size of monolithic MoSi2.
The grain boundary sliding in the composite is significantly suppressed due to the higher grain size and by the presence of SiC particles on the MoSi2 grain boundaries.

Recently, formable high strength DP steels with fine-grained ferrite (<5 µm) have been reported [5], whereas conventional DP steels consist of a coarse recrystallised ferrite (αR).
In order to understand the mechanism of the grain refinement after intercritical annealing and the role of microalloying elements, it would be important to understand the controlling mechanism of grain growth in plain LC steels.
However, the number of studies on the role of γ phase on recrystallisation of α and recovery of deformed α (or subgrain growth within αNR) during intercritical annealing in LC steels seems to be limited, although the situation is similar to the grain growth of coarse αR.
For the discussion of the grain growth mechanism, the following type of equation [12] has often been used, tkrr nn ⋅=− 0 (1) where r is average radius of ferrite grains, r0 is initial radius, and k is a rate constant.
Table 1 Rate constant k estimated by Eq.(2) and the parameters used in the calculation for grain growth of α at 780°C in dual phase steel.

Moreover, nc-Si:H films can be easily grown at relatively low temperatures (100°C-300°C) with the advantage of small energy consumption. nc-Si:H is not a unique, well-defined material but a complex mixture of amorphous and nanocrystalline silicon plus grain boundaries, and also quite a high number of voids.
Therefore, the growth conditions of the film significantly affect its microstructural properties such as the crystalline fraction, the grain size and the amount of grain boundaries [1].
The complicated heterogeneous microstructure of nc-Si:H (a mixture of crystalline silicon grains, grain boundaries and/or a-Si:H ''tissue'', voids) leads to complicated transport properties.
Moreover, not all the grains are conductive and not all the grains present the same conductivity. 1000 nm Figure 2 3D AFM map of a sample of series 1.
Roughness and grain size, for example, significantly change for different substrates.

The different components in RS-SiC can be clearly distinguished due to their different contrast, the bright region is SiC grain and the dark region is Si grain.
Moreover, many cracks are observed on the boundary of SiC grains.
In contrast, SiC grain in RS-SiC was oxidized by anodic oxidation, and Si grain in RS-SiC was almost not oxidized.
Therefore, it is possible that we can remove SiC grain and Si grain in RS-SiC at the same MRR by combing the anodic oxidation and polishing with ceria slurry at the same time, and obtain a smooth surface.
Acknowledgement This work was partially supported by JSPE Grant-in-Aid for Challenging Exploratory Research Grant Number 25630026.