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7. Creep deformation and damage mechanism of compact graphite cast iron with different pearlite contents

Author

Wu Yue, Li Jianping, Chen Hua, Ma Zhijun, Yang Zhong, Guo Yongchun, and Liang Minxian

Subjects
Compacted graphite cast iron, Creep, Interfacial debonding, Pearlite transform, Mining engineering. Metallurgy, TN1-997
Abstract

The creep deformation and damage mechanism of compacted graphite cast iron (CGI) with varying pearlite contents were studied at 450 °C, 500 °C, and 550 °C, with accompanying stress ranges from 40 MPa to 150 MPa. The creep deformation of CGI alloys presents obvious when the temperature exceeds 450 °C. The creep rate exponentially decreases with pearlite contents and the creep mechanism changes from dislocation slip to grain boundary sliding. There are (Ⅰ) intergranular and transgranular cracks, (Ⅱ) interfacial debonding between graphite and matrix, and (Ⅲ) pearlite morphologic transforming in the microstructure of CGI during the creep test. (Ⅰ) and (Ⅱ) are mainly caused by the creep stress and temperature, and (Ⅲ) may be related to plastic deformation. These cracks can interact with each other and accelerate the failure and fracture of materials.

Published
2023
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16. The damage mechanism of tension-tension fatigue interaction with creep damage of the compacted graphite cast iron alloy at high temperatures

Author

Wu Yue, Pei Zehui, Ma Zhijun, Yang Zhong, Guo Yongchun, Liang Minxian, Li Jianping, and Chen Hua

Subjects
compacted graphite cast iron, creep-fatigue interaction, time-dependent deformation, intergranular crack, transgranular crack, Materials of engineering and construction. Mechanics of materials, TA401-492, Chemical technology, TP1-1185
Abstract

The tension-tension fatigue test of the compacted graphite cast iron (CGI) alloy was carried out by RDL100 universal testing at 500 °C and 550 °C, respectively. A tension-tension trapezoidal load is applied to the CGI specimen. Because of the time-dependent deformation at elevated temperatures, the stress–strain curve presents hysteresis loops, and the area of the hysteresis loop increases gradually with continuous cyclic loading and sustained loading times. Intergranular and transgranular cracks in the microstructure accelerate the CGI alloy fracture failure. The fatigue life is sensitive to the short loading time and decreases with the sustained loading time exponentially under the tension-tension fatigue condition. The short holding time has a great influence on the fatigue life of CGI. The fatigue behavior of CGI alloys and the influence of holding time on the fatigue life can be characterized by y = aexp(bx) (a and b are constants, can be fitted through the test data). In addition, the fatigue life of CGI alloy can be predicted by the ductility depletion method. But the equivalent stress amplitude needs to be modified to eliminate the effects of oxidation damage.

Published
2023
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18. The Effect of Heat Treatment on the Microstructure and Mechanical Properties of Plasma-Cladded CoCrFeNiMn Coatings on Compacted Graphite Iron.

Author

Zhang, Bo, Fu, Ruitao, Gao, Peihu, Chen, Baiyang, Naumov, Anton, Li, Fei, Zhao, Daming, Yang, Zhong, Guo, Yongchun, Li, Jianping, Cheng, Lei, Gong, Jinyuan, Liu, Jiawei, and Li, Yu

Subjects
EFFECT of heat treatment on microstructure, MECHANICAL heat treatment, FACE centered cubic structure, SURFACE coatings, WEAR resistance
Abstract

CoCrFeNiMn high-entropy alloy coatings were deposited on compacted graphite iron (CGI) by plasma transfer arc cladding to strengthen and improve the wear resistance (performance) of the surface. The effects of different heat treatment processes on the microstructure and mechanical properties of the CoCrFeNiMn coatings were investigated. Compared with the deposited coating, the single FCC phase in the heat-treated coatings was retained, the grain size of the columnar dendrites decreased, the spacing between the dendrites increased, and the Cr-rich precipitated phase in the grain boundary increased. The heat treatment process had a positive influence on the microhardness and wear resistance of the coatings. The microhardness of the coatings increased after heat treatment. After heat treatment at 660 °C for 90 min, the coating had the highest microhardness of 563 ± 6.9 HV0.2, and it had the best wear resistance. [ABSTRACT FROM AUTHOR]

Published
2024
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27. Oxidation Behavior of Cu-Pb Bearing Alloys

Author

Guo, Qiaoqin, primary, Chen, Jihui, additional, Dong, Yuntao, additional, Yang, Yuting, additional, Li, Jianping, additional, Guo, Yongchun, additional, Yang, Zhong, additional, Yang, Wei, additional, and Xu, Dapeng, additional

Published
2022
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28. Effect of temperature on MgO activity in the CaO-SiO2-MgO-Al2O3 system measured by molten tin

Author

Guo Yongchun, Gao Qiangjian, Jiang Xin, Shen Fengman, Wang Shuo, Zheng Haiyan, Guo Yongchun, Gao Qiangjian, Jiang Xin, Shen Fengman, Wang Shuo, and Zheng Haiyan

Abstract

Blast-furnace slag is one of the main by-products produced in the process of blast-furnace iron-making. Its metallurgical properties have an important impact on the smooth operation and long life of blast furnaces. In this paper, the activity of MgO in a CaO-SiO2-MgO-Al2O3 quaternary slag system was measured using the reference-slag method at 1 773–1 873 K. The effects of temperature on MgO activity and the activity coefficient of Mg in Sn of the CaO-SiO2-MgO-Al2O3 quaternary slag system were discussed. The results showed that when w(MgO)/w(Al2O3) = 0.40, B(w(CaO)/w(SiO2)) = 1.30 and w(Al2O3) = (12 %; 15 %; 18 %; 20 %), the activity of the MgO and the activity coefficient of the Mg in Sn increased with increasing temperature. With increasing temperature, the grooves in the SiO4 tetrahedral structure at wavenumbers of 800–1 200 cm–1 gradually became shallow and flat, indicating that the complex silicate structure synthesised in the form of SiO2 decreased and the activity of the MgO increased. According to the CaF2-MgO binary phase diagram, the dissolution enthalpy of MgO was calculated to be –16.409 kJ/mol. (Authors.), Blast-furnace slag is one of the main by-products produced in the process of blast-furnace iron-making. Its metallurgical properties have an important impact on the smooth operation and long life of blast furnaces. In this paper, the activity of MgO in a CaO-SiO2-MgO-Al2O3 quaternary slag system was measured using the reference-slag method at 1 773–1 873 K. The effects of temperature on MgO activity and the activity coefficient of Mg in Sn of the CaO-SiO2-MgO-Al2O3 quaternary slag system were discussed. The results showed that when w(MgO)/w(Al2O3) = 0.40, B(w(CaO)/w(SiO2)) = 1.30 and w(Al2O3) = (12 %; 15 %; 18 %; 20 %), the activity of the MgO and the activity coefficient of the Mg in Sn increased with increasing temperature. With increasing temperature, the grooves in the SiO4 tetrahedral structure at wavenumbers of 800–1 200 cm–1 gradually became shallow and flat, indicating that the complex silicate structure synthesised in the form of SiO2 decreased and the activity of the MgO increased. According to the CaF2-MgO binary phase diagram, the dissolution enthalpy of MgO was calculated to be –16.409 kJ/mol. (Authors.)

Published
2022

29. Influence of Plasma Arc Current on the Friction and Wear Properties of CoCrFeNiMn High Entropy Alloy Coatings Prepared on CGI through Plasma Transfer Arc Cladding

Author

Gao, Peihu, primary, Fu, Ruitao, additional, Liu, Jilin, additional, Chen, Baiyang, additional, Zhang, Bo, additional, Zhao, Daming, additional, Yang, Zhong, additional, Guo, Yongchun, additional, Liang, Minxian, additional, Li, Jianping, additional, Wang, Wei, additional, Yan, Zhiyi, additional, and Zhang, Lina, additional

Published
2022
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33. Mechanical Properties of Multi-Sized Porous Thermal Barrier Coatings at Micro and Nano Scales after Long-Term Service at High Temperature

Author

Gao, Peihu, primary, Zeng, Shengcong, additional, Jin, Can, additional, Zhang, Bo, additional, Chen, Baiyang, additional, Yang, Zhong, additional, Guo, Yongchun, additional, Liang, Minxian, additional, Li, Jianping, additional, Wang, Wei, additional, Lu, Yongqing, additional, Jia, Lu, additional, and Zhao, Dan, additional

Published
2022
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47. Mechanical alloying of the immiscible Cu-60wt%Cr alloy: Phase transitions, microstructure, and thermodynamic characteristics

Author

Yang Zhong, Jianping Li, Hongjing Wu, Chongfeng Sun, Shengqi Xi, and Guo Yongchun

Subjects
Phase transition, Materials science, Alloy, 02 engineering and technology, engineering.material, 010402 general chemistry, 021001 nanoscience & nanotechnology, Thermal diffusivity, Microstructure, 01 natural sciences, 0104 chemical sciences, Amorphous solid, Differential scanning calorimetry, Chemical engineering, Mechanics of Materials, Transmission electron microscopy, Materials Chemistry, engineering, General Materials Science, 0210 nano-technology, Solid solution
Abstract

Solid state alloying of immiscible alloy systems such as Cu-Cr is an important field of physical metallurgy. Currently, non-equilibrium techniques are successfully applied in the synthesis of Cu-Cr alloys; however, the mechanism of formation of these alloys remains unclear due to the unavailability of data regarding their microstructure evolution and thermodynamic characteristics. In this work, a mechanical alloying (MA) Cu-60wt%Cr alloy is prepared by high-energy milling. The phase transitions, thermodynamic properties, and microstructure of this alloy are analyzed using X-ray diffraction, differential scanning calorimetry, and transmission electron microscope techniques. The obtained results demonstrate that the supersaturated Cr(Cu) solid solution alloy has a supra-nanometer-sized microstructure and is composed of crystalline and amorphous phases. To form the alloy, the localized Cu is first transformed into an amorphous state, then the disordered Cu atoms diffuse into the Cr matrix during the MA process. The diffusivity of Cr atoms in the Cu lattice is significantly hindered, even when the lattice is heavily defected.

Published
2021

48. Influence of 4 wt.% Cr addition on the corrosion-wear synergistic effect for Al2O3/Fe(Al) composites

Author

Bai Yaping, Li Jianping, Huang Qian, Guo Yongchun, Gao Yimin, and Xing Jiandong

Subjects
Materials science, General Chemical Engineering, Metallurgy, General Materials Science, 02 engineering and technology, General Chemistry, Composite material, 010402 general chemistry, 021001 nanoscience & nanotechnology, 0210 nano-technology, 01 natural sciences, 0104 chemical sciences, Corrosion
Abstract

In this work, the corrosion-wear synergistic effect for nanocrystalline Fe(Al), 20 wt.% Al2O3/Fe(Al) composites with and without 4 wt.% Cr in artificial seawater (3.5% NaCl aqueous solution with 60 kg/m3 quartz sand) was investigated. The results showed that the main damage behavior of Al2O3/Fe(Al) composites was a corrosive effect because of its poor corrosion resistance and high hardness, whereas for Fe(Al) material, the main damage mode was a chiseling action by solid particles, due to its relatively low hardness. With 4 wt.% Cr addition, the erosion weight loss at different erosion rates decreased by more than 30%. The Al2O3/Fe(Al) composites had good pure wear resistance, while poor corrosion resistance resulted in an increase in the interaction of corrosion and wear (about 70% of the total damage amount).

Published
2016

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