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Effect of Yttrium and Titanium on Inclusions and the Mechanical Properties of 9Cr RAFM Steel Fabricated by Vacuum Melting
Author(s) -
Zhan Dongping,
Qiu Guoxing,
Jiang Zhouhua,
Zhang Huishu
Publication year - 2017
Publication title -
steel research international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.603
H-Index - 49
eISSN - 1869-344X
pISSN - 1611-3683
DOI - 10.1002/srin.201700159
Subject(s) - materials science , yttrium , vacuum induction melting , ultimate tensile strength , scanning electron microscope , transmission electron microscopy , metallurgy , particle size , carbide , precipitation , alloy , grain size , titanium , composite material , chemical engineering , oxide , nanotechnology , physics , meteorology , engineering
Process of adding yttrium into the melt is not a common method for ODS steel production. In this paper, 9Cr–ODS alloy is prepared by adding Y or Y and Ti into 9Cr steel through vacuum induction melting. Optical microscopy is employed to determine the size and number of particles, scanning electron microscopy is used to examine particle type, and transmission electron microscopy (TEM) is used to determine the compositions of smaller particles. Micron‐size inclusions are observed in the ingots of the #2 and #3 steels; over 30% of the inclusions are 0.5–1 µm in size, and more than 85% are 0.5–3 µm. A large number of Y–Ti–O particles smaller than 0.5 µm are found in the #3 steel, and the density of inclusions reaches 2.69 × 10 19 m −3 . After heat treatment, the particles size decreases, and Ti effectively promotes carbide precipitation. Some nano‐sized Y–Ti–O is detected by TEM. The tensile strength of Y (Y–Ti) alloyed steel reaches 640 (700) MPa at 298 K, and fracturing mainly occurrs via micro‐hole aggregation. At 923 K, the tensile strength of the Y (Y–Ti) alloyed steel reaches 254 (270) MPa. These properties are superior to those of 9Cr steel prepared using the same process.