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When these tiny graphite particles disperse in the Cu grain boundary, pinning effect on the grain boundary is stronger, limits grain boundary migration and velocity, inhibits grain growth.
Meanwhile, in the initial stage of recrystallization of Cu, small graphite particles can act as nucleation, increase the number of nucleation and help for grain refinement. 2.2 Influence of mechanical milling on tensile strength of composites Influence of mechanical ball milling time on tensile strength of composites is shown in Fig. 3.
One reason is that grain and phase are not refined effectively.
After milling for certain time, grain and phase in composite powders are refined to some degree.
Prolonging milling time, Cu grain is finer and graphite distributes in Cu matrix dispersedly.

Through recent industry mergers and acquisitions, the number of players has further reduced to a level where end users have just two or three options if they need to acquire hard alloy billet for further processing.
The selection of hardeners, grain refiners and alloying elements used must be of correct purity and structure to prevent the introduction of inclusions and ensure total solution of the elements and prevent clusters, agglomerates and nucleation zones which will cause grain growth in the as cast metal.
Grain refiner addition is the first step in the process where the specific grain refiner composition is alloy specific.
The use of a high quality grain refiner rod is critical as the titanium performance as a modifier of grain growth during solidification can vary greatly, especially in lower cost rod.
Poor quality grain refiner, incorrect addition rates and incomplete dissolution into the metal can also lead to low pit recoveries through hot and cold cracking of the billets, inclusions in the as cast product in the form or stringers, and other defects as well as non uniform and undesirable grain structure.

Materials Fine-grained concrete.
Table 1 : Properties of different types of fine-grained concrete (mean values, 28d).
The mesh spacing of the fabric has to suit the grain size of the concrete to allow for a full penetration without sieving the grains.
A mesh spacing of 2-3 times the grain size allows for an easy casting of the concrete.
A total number of 137 specimens were tested to examine the load-bearing behavior of the used components, fixing devices and the overall sandwich panel.

As annealing temperatures increased from 260 ˚C to 500 ˚C, the surface morphology of precursors changed significantly, and it is obviously that the number density of the island-type grains decreases (Figs. 2(c)-(h)).
It is clearly noted that the as-sputtered precursor shows cauliflower-like surface texture with the size of grains about 1-3 μm, whereas smaller grains less than 700 nm are detected on the background.
The precursor layers are gradually densified, while the grain size increases.
When annealed at over 400 ˚C, smaller grains less than 200 nm, which covered the cauliflower-like grains, are observed, as shown in Figs. 4(f)-(h).
However, this problem can be overcome by post-annealing treatment [20], and it is found that the number density of the island-type grains degreases in this work, as shown in Fig. 2.

The mean ferrite grain size was determined to be 12 µm and the pearlite grain size 6 µm.
The magnesium specimens subjected to deformation at 0.1 s−1 strain rate and 250 °C are distinguished by a largely advanced DRX process, where the recrystallized grain is observed on both the boundaries of coarse grains and within primary grain areas (Fig. 5b).
Higher work-hardening rates are caused by extensive dislocation development and dislocation pile-up at grain boundaries as high deformation rates have to be accommodated by increasing number of dislocations rather that dislocation glide and climb [16].
Microstructure of the deformed magnesium alloy AZ31 specimen, indicating mechanical twinning (a) and partially dynamically recrystallized grain (b).
Pérez-Prado, Twinning and grain subdivision during dynamic deformation of a Mg AZ31 sheet alloy at room temperature, Acta Mater. 59 (2011) 6949–6962

Low melting point structures formed in the these regions result in localised melting in the grain boundary region and along areas of gross liquid segregation during solution heat treatment, contributing to the poor mechanical properties.
Thixoforming, which was the preferred route during the early development of semi-solid processing, involves the preparation of feedstock which when heated into the semi-solid regions produced the desired spherical primary grain microstructure.
Due to the higher cost of the thixocasting route, the rheoforming route has become the preferred SSM route and is being applied commercially for a small number of applications.
There has been a number of reported studies on the processing of high strength aluminium wrought and casting alloys in search of higher strengths [4,6,7].
In the case of the lower strength 6xxx alloys the problem of incipient melting is not evident but a better understanding of the grain boundary interface and highly alloyed liquid phase in these regions need to be established to improve ductility.

In microalloyed structural steels, boron is generally used to promote the hardenability of steel, that is, a trace amount of boron segregated to the austenite grain boundary, and the nucleation of grain boundary ferrite is suppressed due to the decrease of grain boundary energy [6].
Boron and austenite would form a low-melting eutectic product at the grain boundary in the range of 1150 to 1225 °C.
In the as-casted microstructure of No.1 alloy (see Fig. 1(a)), there are a large number of massive, bar-shaped or granular secondary phases.
In summary, TRIP effect and grain size are the dominant factors controlling the strength and plasticity, while microstructural defects or internal stress are secondary.
Ringer, Role of stress-assisted martensite in the design of strong ultrafine-grained duplex steel, Acta Mater. 82(2015) 100-114

Experiment material and experiment method Experiment material As Hardox 400 wear-resistant high-strength steel of low carbon content, low content of alloying elements, the chemical composition accurate, very low levels of residual elements, controlled by maximizing metallurgy steels S, P, O, N, H and other impurity elements, and the number of inclusions in steel, composition, size, shape and distribution, so it has good mechanical properties[1].
Table 6 Test parameters of oblique Y-groove weld cracking Number Preheating temperature˚C Electriccurrent I/A Voltage U/V Heat input KJ/mm 1# 15 270 30 1.47 2# 50 270 30 1.56 3# 75 270 30 2.04 4# 75 270 30 1.56 5# 100 270 30 1.56 Test results and analysis Microstructure Through microstructure observation in the different regions of the weld, it is organized into base seam weld area and the cover filling layer weld, the base seam weld organization equiaxed ferrite + pearlite, ferrite crystal grains of about 8, it is shown Fig. 2 (c).
Cover the surface layer of cellular dendrite, eutectoid ferrite along prior austenite grain boundaries, the organization is acicular ferrite, granular bainite and pearlite, as shown in Fig. 2(d).
(a) Base metal (100×) (b) Heat affected zone (100×) (c) Backing weld (100×) (d) Covering weld (100×) Fig. 2 Weld and heat affected zone HAZ is massive ferrite and pearlite, grain size decreases, becoming zonal distribution to base metal, the area adjacent to weld and base metal has a clear demarcation and has larger unevenness in the organization in Fig. 2 (b); this is due to the heat-affected zone of the different weld thermal cycle experienced caused, each region will be very different organizations with the decrease of thermal cycles the heat-affected district organization grains become finer [3].
Table 10 Oblique Y-groove cracking statistics Crack location Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 4 Cracks rate, % 0 0 0 0 Surface cracks rate, % 0 0 0 0 Section cracks rate, % 18.3 2.1 3.5 2.6 Conclusion (1) Hardox400 resistant high strength steel with low carbon content, low impurity content, with a special hardening process after continuous rolled with the heat treatment, the steel grain refinement, high purity, good strength and toughness of welded joints, cold cracking sensitivity index lower , the joint cold cracking tendency of small, almost no thermal cracking and reheat cracking

Introduction Attempts at enhancing the fracture toughness of liquid-phase sintered SiC (LPSSiC) and liquidphase sintered SiC-TiC (LPSST) have been the subject of a number of research publications[1 - 7].
In both cases this can be achieved through a controlled coarsening of the SiC grains via an appropriate heat treatment.
This is in line with an argument given by Kim et al[9], in which they claim that the high ductility of TiC, at the high temperature conditions associated with the αβ→ grain coarsening heat treatment, is sufficient to result in a yielding of the TiC grain to a growing SiC platelet.
The use of tailored residual stresses to affect an enhancement in the strength and fracture toughness of different materials has been previously attempted via a number of different means[10, 11].
Strips of material were then cut from the sheets and adjoined to one another in a sequence that conformed to one of a number of stepwise equivalents of selected exponential-type mathematical functions.

Table 1: The ICDD number that was used in analyzing the XRD data No.
The wave number range was set to 400 to 4000 cm-1.
This is the temperature at which the neighbor particles will start to chemically bonded to each other and start to form a smaller grain.
At this stage, the structure will form just like skeletal structure with a weakly bonded small grain.
This stage shows multiple of small grain formation bonded to each other.