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The FESEM and EDS results showed that TiC phases constituted the matrix of the ceramic composites (presented by the dark areas in Fig. 3) while a number of fine TiB2 platelets were embedded in the TiC matrix, and there were also a few of TiB2 platelets embedded in the white area consisting of Ti, W, Cr and C atoms.
In addition, a few of isolated and irregularly shaped a-Al2O3 grains or Al2O3-ZrO2 eutectics were sometimes observed at the top of the sample.
However, because of higher concentration and faster diffusion of C relative to B in liquid Ti alloy as well as the growth isotropy of TiC, TiC grows far faster than TiB2 so that TiB2 platelets are completely surrounded by TiC grains, and the final microstructures consisting of a number of TiB2 platelets embedded in TiC matrix are achieved.
The high hardness and fracture toughness as a result of two kinds of toughening mechanisms: one is crack-pinning by fine, hard TiB2 platelets, and the other is crack-bridging by (Ti,W)C grains, as shown in Fig. 5, so a limited increment in fracture toughness is achieved in the ceramics.
XRD, FESEM and EDS results showed TiB2-(Ti,W)C composites were mainly composed of TiC and (Ti,W)C matrix, in which a number of fine TiB2 platelets were embedded, and a few of isolated, irregularly shaped a-Al2O3 grains and Al2O3-ZrO2 eutectics were also observed at the top of the sample.

The total number of physical sample gradations is 2´6=12, and the number of numerical sample gradations is 4´10=40.
Site compaction of coarse-grained materials [M].
The engineering properties and application of coarse-grained materials [M].
Experimental study on scale effect of coarse-grained materials [D].
Fractal dimensions of soil aggregate-size distributions calculated by number and mass [J].

The size change of precipitates was not obvious under different heat treatment process, but there was a small change in the number of precipitates.
Some studies have shown that the larger the grain size is the longer the incubation period and growth time of precipitates will be.
When the grain size increases from 95μm to 180μm, the incubation period and growth time of precipitates increase from 11s and 90s to 15s and 120s respectively [9].
After the holding temperature of sample 3# was reduced to 530 ℃, the size and quantity of precipitated phase in the base metal were not different from 1 # and 2 #; The surfi-sculpt was still mainly small spherical β”phase, but there was a slightly larger spherical β”phase at the grain boundary.
Corrosion of the sample soaked in 3.5% NaCl solution for 8 hours Under the different heat treatment system, the surfi-scuplt precipitates are mainly spherical, and the number and size change little; However, the precipitation phase of the base metal changes greatly, which has a great influence on the corrosion resistance of the material.

Table 3 Results of orthogonal experiment Test Number Experiment Scheme Factor A Factor B Factor C Appearance Evaluation Joint Tensile Strength /MPa 1 2 3 4 5 6 7 8 9 A1B1C1 A1B2C2 A1B3C3 A2B1C2 A2B2C3 A2B3C1 A3B1C3 A3B2C1 A3B3C2 1 1 1 2 2 2 3 3 3 1 2 3 1 2 3 1 2 3 1 2 3 2 3 1 3 1 2 B B B C B B A A B 252.19 238.22 234.52 136.31 306.51 272.84 332.19 301.33 322.60 Note: A: weld surface forming good; B: weld surface forming general; C: weld surface forming poor Orthogonal test result analysis is shown in Tab.4, including Km (m = 1 ~ 3) for A, B and C factors of the mth of the corresponding level joint tensile strength average, the range R for K1, K2, K3,the number of 3 maximum and minimum difference, the greater the range, the factors that influence the joint tensile strength is larger.By three factors of the range all level analysis shows, rotating speed influence the joint tensile strength seriously, and heating temperature
Fig.1 Low carbon steel friction stir welding’s weld crossing section shape and tensile samples size Then,we select number 7 samples of tensile strength of the highest as material to analyse.
Q235 steel is constituted by ferrite (white) and tiny pearlite (black). b is the heat affected zone microstructure, which is composed by the ferrite (white) and pearlite (black), but slightly bigger than the base material zone in grain size.
At the same time, it contacts the base material,whose heat dissipating quickly.The retention time of high temperature is short.The grain grow up, but they grow up littlely. c is the thermo-mechanically affected zone microstructure,which is constituted by the long strip ferrite (white) and bulky pearlite (black).
The stir zone is affected by the mechanical stir function strongly, producing more heat, concentrating heat, appearing more obvious work-hardening phenomenon.There is a complete dynamic recrystallization under the strong stir function of the stir needle.So grain become more small after cooling.According to these reasons ,the area’s microhardness improved on average by 12% to the base material zone.The microhardness of the thermo-mechanically affected zone and the heat affected zone decreases compared to the mother zone, this is due to grain growing in the welding process after heating.

Table 1 Powder characteristics Feedstock powder Feedstock size/μm WC grain size Conventional WC-12Co 5～35μm 1～2μm Coated samples were obtained from a commercial coater.
Secondly, the growth of grains and oxidation of carbon further promotes the WC to dissolve into the Co-rich matrix, followed by the heated powder bumping into the substrate and cooling down.
The results show that the main factors affecting the indentation crack propagation and fracture toughness are WC grain size, binder phase content and the performance of each phase, etc..
For the WC-Co cemented carbide, the fracture toughness increases with the binder content increasing when the WC grain size is the same.
WC particles contact with each other, which weakens the connecting role of grain boundary and affects the strength and toughness of the coatings.

Despite a large number of studies in this direction, a significant part of them is devoted to the operating conditions and characteristics of the coatings regardless of the method of its application, for example [3].
The grain size is 30÷40 points in the frequency range 40÷60 Hz (Fig. 2).
The grain size was determined with an increase of ´150 by measuring the average nominal diameter (dnom) of 140÷160 austenite grains.
Kanjilal, Influence of modes of metal transfer on grain structure and direction of grain growth in low nickel austenitic stainless steel weld metals, Materials Characterization. 102 (2015) 9–18
Mohanty, A modified analytical approach for modeling grain growth in the coarse grain HAZ of HSLA steels, Scripta Materialla. 50 (2004) 1007- 1010

Although the average grains size of nano scale exceeds 100 nm in most of the sintered samples, there still grains smaller than 100 nm can be observed.
In addition, nano grains were obviously surrounding the micro grains.Fig. 3 (d) shows the microscale grains (M) were completely surrounded by nanoscale grains (N).
%which caused by the increase of the average grains size of microscale.
In addition increasing the amount of N leads to increase the number of grain boundaries through which the fracture toughness is reduced.
Summary A multiscale microstructure in which the micro size grains were surrounding by nano size grains was formed using ball milling and PAS.

Sieve analysis is one of the method techniques used for separating grains.
The distribution of particle size is determined by the size ranges that cover most sizes present in the sample [6]. grain-size analysis determines the proportional size of different grains distributed in specific size ranges. sieving processes are carried out on dried materials [7].
Mineral composition of silica sand Grain analysis of the sample The grain analysis process was carried out with a representative sample using sieves with holes 850, 600, 250, 150, and 75 microns to identify the grain sizes of the ore (Table 2).
Grain analysis of ore and ratio of iron oxide Grain size μ Weight ratios % Cumulative weight ratios (for passers) % Fe2O3% Iron oxide distribution ratio in the ore % + 850 1.60 100 0.1 1.76 - 850 + 600 0.76 98.40 0.05 0.408 - 600 + 250 70.5 97.62 0.09 69.066 - 250 + 150 26.88 27.02 0.117 33.89 - 150 + 75 0.1 0.16 0.18 0.1841` - 75 0.04 0.05 0.08 0.04 Weight percent grain size μ Fig. 3.
General Company for Geological Survey and Mining, report number 2888, 2005

Ti has a strong affinity with O[14], small amount of Ti can achieve grain refinement and improve the performance of the steel.
The number of inclusions smaller than 2μm accounted for 91.6% of the total number in Al deoxidation condition.
Number of inclusions smaller than 2μm accounted for 94.5%.
Number of inclusions smaller than 2μm accounted for 95.2%.
The tiny nucleation cores not only can refine grains of the steel, but also improve the strength and toughness.

Defect Type Main Physical Parameters The Images of Defect Models 1 Soaking joint Cable inside joint was soaked in water for 24h,and water was injected during installation 2 Incision on cable Breadth and depth of incision is 10 cm and 2mm.Length of outer shielding lay wound is 5cm； 3 Puncture on cable Diameter and depth of puncture are 3 cm and 4mm. 4 Sharp insulation screen on outer semiconductive layer Two sharps are isosceles triangles which bottom edge is 4mm,height is 1cm, spacing is 8mm. 5 Conductive grain on the interface of composite insulation Area of conductive grain is about 5cm×7.5cm 6 Prefabricated unit offset Stress cone is 5mm away from standard location.
Parts of representative spectrum diagrams are given as follows: Table2 Pulse and frequency spectrum of typical defects The spectrum of soaking joint defect The spectrum of incision defect The spectrum of puncture defect The spectrum of sharp insulation screen defect The spectrum of conductive grain defect The spectrum of prefabricated unit offset defect Table3 Q-Φ spectra of typical defects The spectra of soaking joint defect The spectra of incision defect The spectra of puncture defect The spectra of sharp insulation screen defect The spectra of conductive grain defect The spectra of refabricated unit offset defect In this section, the characteristic spectrum diagrams of typical defects have been concluded, discharge signals in 6 samples of typical defects were acquired by CPDM in the pure electromagnetic laboratory, typical discharge signal samples were achieved in time domain, frequency domain, and corresponding Q-Φ spectra, it could achieve the obvious differences
These statistical estimators are kurtosis, skewness, Cross Correlation, charge asymmetry; these are defined by the following expressions [9]: Sk=i=1Nxi-μ3f(xi)/[σ3i=1Nf(xi)] (1) Where xi : sample value of the distribution μ : mean value N: number of samples σ:standard deviation Skewness describes the asymmetry aspect with respect to the normal distribution.
W number of samples of the wave period Asymmetry represents the charge transfer differences in the positive and negative polarity discharge events; this feature has the following expression: Asy=N2i=1N2xi-/N1i=1N1xi+ (4) Where N1 and N2 are number of sampling intervals in the positive and negative half-wave period.
Table 2 Representative characteristic parameters of various defects Soaking joint defect Cable incision defect Cable puncture defect Sharp screen defect Conductive grain defect Cutting into main insulation Phase range of discharge 10º~100º 200º~280º 0 ° ~60 ° 180 ° ~230 ° 0º~90º 180º~270º 100º~180º 220º~300º 50º~150º 220º~270º 20º~120º 190º~300º Phase of peak 92º and 268º 31 ° and 204 ° 36 ° and 207 ° 89º and 253º 96º and 272º 95º and 266º Discharge magnitude 982 pC 3.5 pC 12.4 pC 172 pC 102 pC 9 nC Repetition rate 81 PDs∕s 48 PDs∕s 66 PDs∕s 30 PDs∕s 32 PDs∕s 35 PDs∕s Rise time 21ns 33ns 227ns 143ns 279ns 18ns Fall time 36ns 85ns 485n 189ns 364ns 35ns Skewness 1.021(+) 1.153(-) 0.598(+) 0.526(-) 1.4244(+) 1.5029(-) -1.717(+) -1.565(-) 1.253(+) 1.463(-) 0.847(+) 0.614(-) Kurtosis -0.798(+) 1.02(-) -0.337(+) -0.382(-) -0.7411(+) -0.6458(-) 1.266(+) 2.195(-) 0.491(+) 0.422(-) 2.267(+) 2.829(-) Cross Correlation 0.316 0.905 0.7869 0.95 0.543 0.858 Asymmetry 1.642 1.033