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The support of the matrix to hard grains is damaged greatly.
Around the grain dendritic carbide separated out.
grain.
The dissolving of tungsten carbide particles in MIG welding is serious and a large number of C atoms and W atoms have entered matrix to make the layer have the highest hardness.
WC/W2C grains play a key role in improving abrasion resistance.

Introduction The sequential or simultaneous action of plastic deformation and electric current in different alloys, including shape memory TiNi alloys, leads to a number of interesting phenomena.
In the austenitic alloy after EPR (е=1.2) annealing at 500°С forms the nanograined structure with a mean grain size of 80 nm (Fig. 2a).
In the martensitic alloy the same annealing leads to a grain size of 100 nm (Fig. 2b).
However, a smaller grain size of 60 nm can begin to form at 450 °С (Fig. 2c).
The average grain size in the Ti50.0 Ni50.0 alloy is lower that that in the Ti49.2Ni50.8 alloy. 4.

Fig. 2(b) shows the spinel grains doesn’t bond tightly and only part direct binding exist between grains showing the sintering was incomplete.
From the Fig. 3(a) it could be observed that the specimen T4 has denser structure, less porosity and high direct bonding between the grains.
It can also be seen from Fig. 3(b) that the spinel grains bond tightly and had high direct bonding showing the sintering was well.
More cracks exist especially between the large grains.
That small spinel grains have high direct bonding showing well sintering, but large grains did not bind well.

The same is true of press and sinter powder Injection molding processes because of the shape complexity and dimensional tolerances which cannot be achieved without extensive machining operations Powder injection molding (PIM) is an emerging technology for the cost-effective production of large numbers of small metals parts.
It is thought that the porosity is reduced when the sintering temperature increased and this lead to the formation of grain.
The grain boundary formation is a result of the grain coalescence process and though the orientation of the microstructure is slightly different, they essentially have a similar grain shape.
Microstructure of sintered Inconel 718; Sample A (a) and Sample B (b) Observations over a range of magnifications reveals that increasing temperature has significantly improved the homogeneity of the microstructure, specifically the pore size is reduced and the grain are more evenly distributed.
The high densification of sample B was achieved due to the particles which became interconnected signifying that under the condition of high temperature, grain displacement and plastic deformation occur which eliminating the pores, and therefore grain growth takes place along with the densification during the sintering process[5].

Scandium is an effective grain refiner and increases the recrystallization temperature in aluminium alloys.
The addition of scandium has changed grain structure of Al-Si-Mg alloy from columnar to fine equiaxed.
First, grain refinement during casting or welding, second precipitation hardening from Al3Sc particles and lastly, grain structure control from Al3Sc dispersoids [4].
Scandium when added in small concentrations is known to refine the grain structure of cast metal and to form a supersaturated solid solution upon solidification.
Limmaneevichitr , Grain refinement mechanism in Al-Si-Mg alloy with Scandium, Journal of alloy and Compounds, 542 (2012) 177-186

MgO is a traditional additive for Al2O3 because it can reduce the sintering temperature and decrease grain size.
The amount of MgO was varying from 0 to 5vol%, with the material numbers changing from AC2NM0 to AC2NM5, as shown in Table 1.
The drastic decrease of fracture toughness is basically related to the small grain size of the grain boundary.
Chantikul et al.[11], the intrinsic toughness diminishes as the grain size decreases due to the reduced load bridging capability of the smaller grain bridges.
That is to say, MgO could inhibit grain growth of Al2O3-TiN-TiC ceramic composite, eventually form homogeneous and dense ceramics.

The grain refinement effect increases and then decreases with increasing pressure.
And these defects can provide a number of new nucleation sites, resulting in increasing neucleation efficiency[9].
The reason for this is that the atoms on the grain boundaries are disordered and many vacancies exist, resulting in the lower density and the higher energy than that in the grain.
And the grain with a higher potential would be protected as a cathode.
It is well known that the finer the grain of the alloy is, the larger the proportion of grain boundary area is.

The LSMO properties are modified by sintering temperature, which ruled the grain size and grain boundary properties [3, 4].
The SEM images showed LSMO samples have different grain size where the grain size increases with increasing sintering temperature.
This implies a decreasing number of grain boundaries by increasing sintering temperature, in agreement with Ref. [3].
Table 1 summarized the properties of grain size, µHC and MSP of LSMO samples.
We remark that MR values are not ruled by the physical properties i.e. grain size as reported in Refs. [3].

The resultant thin films were a mixture of monoclinic and tetragonal phases of WO3 and, after being pretreated at 600°C and sintered at 650°C, the average grain size of the polycrystalline films was about 500 nm.
It has been noted that WO3 shows a good property for gas sensing to various gases such as H2S, NOx, trimethylamine and a number of other organic compounds gases.
Three most intense dif- fraction peaks were located at 2θ angles of 23.15°, 23.59° and 24.40° respectively, which were identified with JCPDS number of 830951 for monoclinic phase.
Moreover, another intense diffraction peak could be observed at 2θ angles of 23.74°, which was identified with JCPDS number of 181417 for tetragonal phase.
However, increasing clcination temperature higher than 650°C would result in the increase of the grain size, consequently the decrease of surface area.

And, the adding of rare earth element in Al-Fe alloy can fine organization and strengthen the grain boundary.
So the growth of iron-rich phase can be limited by the large number of new nuclei and organizations of alloy can be relatively refined [4].
And the adding of La can refine the grain and improve the performance of Al-Fe alloy [5].
Thus, the size of grain cell was around 200-400 nm in the free side.
Most of the spherical particles were distributed in the dendritic grain boundaries, a small number were distribution within the crystal cell.