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1

Effect of Ti Addition on the Residual Aluminium Content and Mechanical Properties of the B4C-Al Composites Produced by Vacuum Infiltration

100%

Xiaozhou C. , Chao W. , Xiangxin X. , Gongjin C.

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tom Vol. 60, iss. 4

2493--2498

EN

The effect of Ti addition on the residual Al content and mechanical properties of B4C-Al composites fabricated by vacuum infiltration was investigated in the present study. The B4C-Al composite materials were fabricated using [Ti+B4C] preforms preheated at 1700ºC for 1 h and Al alloys infiltrated in vacuum atmosphere at 1100ºC for 2 h. The phase composition indicated that TiB2 has high wettability to Al as a result of the preheating. SEM and EDX results revealed a number of Al dimples are on the fracture surface due to the existence of TiB2. When the content of added Ti increases to 30%, the [Ti+B4C] preform is characterized by a minimal porosity (33.11%) and a maximal density, a corresponding amount of residual Al of 33.11% and a minimal fracture toughness (5.03 MPa·m1/2) with a hardness of up to 63 HRC. The residual Al and the mechanical properties of the composite material preform were determined by the Ti content of the preform.

PL

Zbadano wpływ dodatku tytanu na resztkową zawartość Al i właściwości mechaniczne kompozytów B4C-Al wytworzonych przez infiltrację próżniową. Kompozyty B4C-Al lzostały wytworzone przez infiltrację stopów Al, w próżni, w 1100ºC przez 2 godziny, do wstępnie wygrzanych w 1700ºC przez 1 godzinę preform [Ti+B4C]. Faza TiB2 charakteryzuje się wysoką zwilżalnością przez Al na skutek wstępnego wygrzania. Wyniki analizy SEM i EDX ujawniły pewną liczbę wgłębień Al znajdujących się na powierzchni pęknięcia z uwagi na obecność TiB2. Gdy zawartość dodanego Ti wzrasta do 30%, preforma [Ti+B4C] charakteryzuje się minimalną porowatością (33,11%) i maksymalną gęstością, odpowiednią ilością resztkowego Al tj. 33.11%, minimalną odpornością na kruche pękanie (5,03 MPa·m1/2), i twardością do 63 HRC. Resztkowe Al i właściwości mechaniczne materiału kompozytowego preformy determinowane są przez zawartość Ti w preformie.

2

The effect of Ti addition on the microstructure and fracture toughness of BN-Al composite materials synthesized by vacuum infiltration

88%

Chao W. , Xiangxin X. , Xiaozhou C. , He Y. , Gongjin C.

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tom Vol. 58, iss. 2

509--512

EN

In this paper, we studied the effect of Ti addition on the microstructure and fracture toughness of Boron nitride- Aluminum (BN-Al) composite materials that were synthesized by vacuum infiltration. The BN-Al composite materials were fabricated by preheating the [Ti+BN] preforms at 1700º for 1 hour before Al alloys were infiltrated into the preforms in a vacuum atmosphere at 1100º for 2 hours. X-ray diffraction (XRD) patterns showed that the diffraction peaks of titanium diboride (TiB2) appeared when the [Ti+BN] preforms were preheated. It is thought that metal Al protected are visible and this could be achieved by the generation of TiB2 when Al infiltrated into the preform from fractography. The matching fracture toughness of the [Ti+BN] preforms gradually improve when Ti content was increased.

PL

W niniejszej pracy badano wpływ dodatku Ti na mikrostrukturę i odporność na pękanie kompozytów aluminium-azotek boru (BN-Al), które zostały zsyntetyzowane przez infiltracje w próżni. Kompozyty BN-Al zostały wykonane przez podgrzewanie preform [Ti+BN] w 1700ºC przez 1 godzinę, po czym stopy aluminium infiltrowano do preform w atmosferze próżni w temperaturze 1100ºC przez 2 godziny. Dyfrakcja rentgenowska (XRD) wykazała, że piki dyfrakcyjne diborku tytanu (TiB2) pojawiły się gdy preformy [Ti+BN] zostały podgrzane. Uważa się, że aluminium jest chronione co widoczne jest na przełomach i może to być osiągniete przez wytwarzanie TiB2 gdy Al przeniknęło do preformy. Odporność na pękanie preform [Ti+BN] stopniowo poprawia się, gdy zawartość Ti została zwiększona.

3

Vertical distributions of phosphorus fractions in sediments of three typical shallow urban lakes in P.R. China

88%

Chao W. , Jin Q. , Zhi-yong G. , Li Z. , Xiao-chen L.

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nr 1

155-162

EN

Sediment cores were sampled from three typical shallow urban lakes in China. The Standards, Measurements and Testing (SMT) programme, proposed by the European Commission, was employed to characterize the vertical distributions of phosphorus fractions in sediment profiles. The results showed that TP contents ranged from 1,198.9 to 1,897.3, 1,289.1 to 1,652.1, and 611.7 to 760.3 mg kg⁻¹ in sediment profiles of Daming Lake, Mochou Lake, and Xuanwu Lake, respectively. Within the 50-cm sediment profiles, phosphorus distributed mainly in IP, and the OP contents only accounted for 9.7%-16.3% of TP. For IP in sediments, the AP was the predominant fraction for Daming Lake and Mochou Lake, accounting for 92.8%, and 71.4%, respectively. While for Xuanwu Lake the proportion of NAIP to IP was higher than that of AP (41.7%±6.0%), indicating that the Xuanwu Lake was polluted more heavily than the other two lakes. The phosphorus concentration in pore-water (TDP) correlated significantly to the P fractions in sediments, especially to the OP and NAIP contents, which could be predicted by: TDP (mg L⁻¹) = 0.005 OP (mg kg⁻¹) – 0.001 NAIP (mg kg⁻¹) + 0.138 (R² = 0.836, P<0.01). The physicochemical properties of sediments presented significant correlation to the contents of P fractions, highlighting the importance of the physicochemical properties of sediments for the phosphorus fraction distributions in lake sediments.

4

A transformer winding deformation detection method based on the analysis of leakage inductance changes

75%

Jiansheng L. , Fengbo T. , Chao W. , Yuncai L. , Peng W. , Mengzhou Z. , Miao Y.

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tom Vol. 64, nr 2

333--346

EN

The detection of transformer winding deformation caused by short-circuit current is of great significance to the realization of condition based maintenance. Considering the influence of environment and measurement errors, an online deformation detection method is proposed based on the analysis of leakage inductance changes. First, the operation expressions are derived on the basis of the equivalent circuit and the leakage inductance parameters are identified by the partial least squares regression algorithm. Second, the amount of the leakage inductance samples in a detection time window is determined using the Monte Carlo simulation thought, and then the samples in the confidence interval are obtained. Last, a criteria is built by the mean value changes of the leakage inductance samples and the winding deformation is detected. The online detection method considers the random fluctuation characteristics of the leakage inductance samples, adjust the threshold value automatically, and can quantify the change range to assess the severity. Based on the field data, the distribution of the leakage inductance samples is analyzed to obey the normal function approximately. Three deformation experiments are done by different sub-winding connections and the detection results verify the effectiveness of the proposed method.