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Effect of Cobalt on Microstructure and Mechanical Properties of Invar Alloy

  • Cuixin Chen
  • Baojun Ma
  • Sainan Miao
  • Baoxi Liu
Conference paper
Part of the Lecture Notes in Mechanical Engineering book series (LNME)

Abstract

Due to low coefficient of thermal expansion (CTE), Invar alloy is widely used in Liquefied Natural Gas (LNG) carrier, long distance transmission lines and so on. However, the coarse grain and low hardness restrict the further application. In the present study the samples were prepared by vacuum arc furnace. The effect of cobalt on microstructure and mechanical properties were explored. The results showed that the microstructure without cobalt was mainly composed of coarse columnar crystals with heterogeneous dimension distribution, and average grain area was 289 μm × 189 μm. For the sample with 0.2 wt% cobalt the microstructure was more uniform and the average grain area was 260 μm × 166 μm. In addition, lots of cellular substructure formed in the columnar dendrite with different shapes dislocation etch pits. The CTE decreased with the addition of cobalt, especially when the content of cobalt was 0.2 wt%. Compare to the sample without cobalt the microhardness with cobalt addition of 0.2 and 4 wt% are 193 and 170 HV, increased by 25 and 10% respectively. It can be concluded that the microstructure and mechanical properties can be changed by controlling the content of cobalt under the condition of rapidly cooling condition.

Keywords

Invar alloy Vacuum arc melting Crystalline organization Grain area Hardness 

Notes

Acknowledgements

The present authors are thankful for the financial support provided by National Natural Science Foundation of China (No 51304059).

Author Contributions

C. X. Chen: designing the experiment approach and executing part of the experiment processing; B. J. Ma: executing most part of the experiment processing; S. N. Miao: for mechanical property test; B. X. Liu: for theoretical analysis.

Conflicts of Interest

The authors declare no conflict of interest.

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Copyright information

© Springer Nature Singapore Pte Ltd. 2018

Authors and Affiliations

  1. 1.School of Materials Science and EngineeringHebei University of TechnologyTianjinChina
  2. 2.Tianjin Key Laboratory of Laminating Fabrication and Interface Control Technology for Advanced MaterialsHebei University of TechnologyTianjinChina
  3. 3.Research Institute for Equipment Materials, Hebei University of TechnologyTianjinChina

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