J. Mater. Sci. Technol. ›› 2020, Vol. 47: 68-75.DOI: 10.1016/j.jmst.2020.02.010

• Research Article • Previous Articles     Next Articles

The influence of microtexture on the formation mechanism of nodules in Zircaloy-4 alloy tube

Yingdong Zhanga,b, Fusen Yuana,b, Fuzhou Hana,b, Muhammad Alia,b, Wenbin Guoa,b, Geping Lia,*, Chengze Liua,b, Hengfei Gua,c   

  1. aInstitute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China
    bSchool of Materials Science and Engineering, University of Science and Technology of China, 96 JinZhai Road, Baohe District, Hefei, Anhui 230026, China
    cUniversity of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China
  • Received:2019-10-25 Revised:2019-12-11 Accepted:2020-01-07 Published:2020-06-15 Online:2020-06-24
  • Contact: Geping Li

Abstract:

Corrosion resistance of Zircaloy-4 alloy tube in superheated steam at 673 K/10.3 MPa is anisotropic. A part of the surface undergoes uniform corrosion while the other suffers nodular corrosion. Narrow and wide nodules are observed after an exposure period of 3 and 30 days, respectively. A new matrix transformation method is established in order to study the formation mechanism of nodules in the cross-section (CS) of Zircaloy-4 alloy tube using the EBSD technique, while the CS perpendicular to axial direction (AD). The results reveal that the microtexture is a key factor behind the two types of corrosion. Furthermore, the oxide layers grow anisotropically over the corroded surface. A thick oxide layer forms over the nodular corrosion region on the grains with c-axis oriented in the range of 40° around tangential direction (TD), whereas a thin oxide layer over the uniform corrosion region is detected on the grains with c-axis oriented in the range of 68° around TD. In short, the anisotropic growth of oxide layer was caused by the change of microtexture of the Zr-4 alloy tube, and this anisotropic growth of oxide layer contributed to the nodules formation.

Key words: Zircaloy-4 alloy, Microtexture, Nodular corrosion, EBSD technique, Matrix transformation method