REAEARCH PAPER |
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Influence of Ni on the Thermal Stability of a New Die Casting Steel |
ZENG Yan, WU Xiaochun, XIA Shuwen, ZUO Pengpeng
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School of Materials Science and Engineering, Shanghai University, Shanghai 200072 |
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Abstract The thermal stability and microstructure evolution of a new die casting steel containing 1% (mass fraction) nickel and without nickel were comparatively studied. Two kinds of steels were quenched in the same process, following by several times of tempering to achieve similar hardness. The thermal stability experiment of the materials was carried out at 600 ℃. SEM (scanning electron microscopy) and TEM (transmission electron microscopy) were employed to compare the microstructure evolution of the two materials during the thermal stability test, in order to explore the effect of Ni on microstructure of the material. The results showed that in the process of austenitizing, Ni retarded the dissolution of carbides, and the undissolved carbides at the grain boundaries prevented the growth of the austenite effectively, so that the quenching temperature could be increased. When quenched at the same temperature, the carbides in SDYZ1 could not dissolve in the matrix adequately, which reduced the precipitation strengthening effect of secondary carbides, and then resulting in a sharp decline of the hardness in the early stage of the thermal stability experiment. The advantage of Ni to improve the thermal stability of the material may need to be reflected at a much higher quenching temperature.
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Published: 25 August 2017
Online: 2018-05-07
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