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After being treated, the samples’ microstructure changes of accumulated fatigue damage cycling to a number of times were observed by SEM, and the mechanism of repairing fatigue damage was studied.
Thinning grain can be obtained by tempering, so that the numbers of grain will increase in a certain volume of the grains.
The same amount of distortion can be assumed by more grains, get more uniform deformation, which will not cause stress concentration seriously, and the metal has a good plastic.
The repair of fatigue damage mainly uses the recovery phase which microstructure changes in. the phase of restoration is the process before serious distortion of new grain.
From the graph, in early fatigue life cycle, distribution state of carbide particle and dislocation inside grain is disordered.

There are number of factors controlling this issue as discussed hereafter: Critical size of nanoparticles.
Nanoparticle addition in the MMCs is expected to offer grain refinement due to pinning effect in the grain boundaries.
However, there are reports which show the inability of nanoparticles to serve as either nucleation sites or obstacles to grain growth during solid state cooling and no significant change in grain size compared to the corresponding monolithic alloy [17, 24].
The micro-voids nucleates at region of localized strain discontinuity like second phase particles, inclusion and grain boundary dislocation piles up.
The size of the dimples on a fracture surface depends on the number and distribution of micro-voids that are nucleated.

The energy of grain boundary atoms is higher than the energy of atoms in the crystal, and the grain boundary atoms are more active and easier to diffuse.
At the same time, the grain boundary can provide a heterogeneous nucleation core.
So comparing the three alloys, the number of MgSi phase of the A alloy is significantly more than other three alloys.
However, when the Mg/Si ratio is reduced to 0.9, a large number of phases with large size appear in the alloy crystals, which makes a significant decrease in alloy elongation. 3.
At the same time, the β" phase density is high, and there is no obvious elemental Si in the grain boundaries.

Fig.1 Optical microstructure of casting CuZn37Mn3Al2FeSi alloy (a: rapidly cooling ,b: nature cooling) It can be seen from the figure that the wear resistant phase’s distribution in casting organizations has no obvious direction, and its size is about (5-10) um × (10-50) um bar, among which a small number of hexagons. casting organizations are small under rapid water cooling condition, especially the wear resistant phase of ferro-silico-manganese, with size (3-8) um ​​× (10-30) um; In air-cooled conditions, the size of both the grain and ferro-silico-manganese are relatively thick, a few even to 40-60um.
When the temperature rises to 350℃, large amounts of needle α-phase precipitates from the grain interior, there is a small amount of globular α phase at grain boundary; Aging at 380℃ and 420℃ for 1 hour, α-phase precipitates from the grain interior and there are many globular α phase at grain boundary, and the number was significantly increases; When the temperature is higher than 460℃,the needle α-phase is very few, and the intragranular α-phase becomes globular; aging at 520℃, no precipitation of α phase, and the grain was grown visibly, and the grain boundary becomes irregular；The ferro-silico-manganese phase changes a little during the whole heat treatment process.
Therefore, the best precipitation temperature of α-phase is between 350℃ and 460℃, and with temperature rise, distributional pattern of α-phase changes from a single needle precipitating from the grain interior into needle and globular precipitating simultaneously.

However, biological apatites differ chemically from stoichiometric HA in that they contain a number of additional trace elements substituted into the HA lattice.
The section of CHA1 is dense and uniform without obvious pores and the grain size is about 500nm.
The grain size of CHA2 has obvious increase with an average of about 2 mm; the grain size of CHA3 is comparable to that of CHA2, but CHA3 appears lots of pores with hundreds of nanometers.
Carbonate substitution reduces the sintering temperature and grain size.
The grain boundaries in fine-grained materials make the crack difficult to expand, resulting the flexural strength of CHA1 higher than that of CHA2.

It is believed that the increase in transmittance following HIPing was attributed to a growth in the grain size and reduction in the number of grain boundaries.
The specimens displayed uniform grains of about 50 µm.
Fig. 5B shows large grains with porosity distributed within the grains.
It is believed that these large grains traping the porosity.
Elimination of these grains should increase the strength of the spinel significantly and the optical transmittance may increase by elimination the porosity within the large grains.

The type I sandstone is the felsic fine-grained sandstone (shown in Fig.1 (a)), and the type II sandstone is weak altered argillaceous sandstone (shown in Fig.1 (b)).
(a) crossed polarizer (b) monopolarizer Fig. 2 Micro-structural pictures of type I sandstone (a) crossed polarizer (b) monopolarizer Fig. 3 Micro-structural pictures of type II sandstone The mineral signed by number 1 in picture (a) of Fig.3 is feldspar, mineral signed by number 2 is quartz, mineral signed by number 3 is zircon, and mineral signed by number 4 is muscovite.
The mineral signed by number 1 in picture (b) of Fig.3 is grain crumbs and mineral signed by number 2 is clay cement.
The mineral signed by number 1 in picture (a) of Fig.4 is quartz and mineral signed by number 2 is sericite cement (clay).
The mineral signed by number 1 in picture (b) of Fig.4 is grain dust and mineral signed by number 2 is cement.

When pulled in TD, the Goss oriented grains are much harder than the cube oriented grains, and hence retains a higher surface level than the cube oriented grains.
∑β βαβ α γ= &hg (4) The αβ h is n×n hardening matrix, where n is the total number of slip system.
The initial grain size also influences the final grain size after processing.
The columnar structured specimens have larger grains, because the initial grain size of Fig. 1.
For AA6022, the band-type clusters of Goss-oriented grains shrink in RD more than the clusters of cube oriented grains, resulting in higher surface profiles along the Goss-grain banded clusters and lower surface profiles along the cube-grain banded clusters.

The domain of high cycle fatigue (HCF) corresponds to small applied stress with resultant high number of cycles-to-failure (Nf > 10 5 cycles).
This partially explains the scatter that is normally observed at the microscopic level and quantified as number of cycles-to-failure [11].
(a) The recrystallized grains.
The microscopic cracks were dispersed both through the grain and along the recrystallized grain boundaries (Figure 12c).
The cracking was both through the grain and along the grain boundaries with the presence of dimples adjacent to the grain boundary cracks reminiscent of locally brittle and ductile failure mechanisms.

The dressing efficiency is higher under the lower rotate speed in a special range, is related non-linearly with the feeding speed because of the consume of the truing tool, and is lower under higher density and smaller grain size of the wheel structure because there are more micro cutting edges.
Table 1 Experimental Condition Machining Tool Y7125 (1415r/min, 1.5 kW) Saucer Resin Bond Diamond Wheel ( � 400 mm, 20 mm width and 3 mm thickness of the abrasive layer) No.1: 75% Density, 150 # Grain Number No.2: 100% Density, 200 # Grain Number Dressing Apparatus Special Apparatus Fixed on Y7125 Dressing Tool FOULKERS Truing Tool (d=9.525 L=44.45) Frequency Convertor FVR2.2E11S-V(0~400 HZ) During the practical experiment, the length of the truing tool consumed was equal to the dressing depth ad after to-and-fro feeding.
The mode of feeding from the outside and the inside of wheel in turn Journal Title and Volume Number (to be inserted by the publisher) 83 was used to obtain the evener work face after dressing
From Eq.2, the total amount of the diamond grit in the abrasive layer is increased when the density and the grain fineness number of the wheel are chosen larger one.
The efficiency is lower under higher density and smaller grain size of the wheel structure. 3.