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Phase Transformation and Texture in Hot‐Forged or Annealed Liquid‐Phase‐Sintered Silicon Carbide Ceramics
Author(s) -
Xie RongJun,
Mitomo Mamoru,
Kim Wonjoong,
Kim YoungWook,
Zhan GuoDong,
Akimune Yoshio
Publication year - 2002
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2002.tb00111.x
Subject(s) - materials science , silicon carbide , annealing (glass) , ceramic , forging , texture (cosmology) , metallurgy , sintering , carbide , composite material , phase (matter) , hot pressing , grain boundary , microstructure , chemistry , organic chemistry , artificial intelligence , computer science , image (mathematics)
Starting from three powder mixtures of 80 vol% SiC (100α, 50α/50β, 100β) and 20 vol% YAG, liquid‐phase‐sintered silicon carbide ceramics were prepared by hot pressing at 1800°C for 1 h under 25 MPa, and then by hot forging or annealing at 1900°C for 4 h under an applied stress of 25 MPa in argon. The phase transformation and texture development in the as‐hot‐pressed, hot‐forged, and annealed SiC ceramics were investigated via X‐ray diffraction (XRD) and the pole figure measurements. The 6H → 4H polytypic transformation was observed in samples consisting of both α‐ and β‐SiC phases when subjected to compressive deformation but absent in the case of annealing, suggesting the deformation‐enhanced solubility of aluminum in SiC. Deformation was also found to enhance the 3C → 4H transformation in the sample containing entirely β‐phase, which is due to the accelerated solution‐precipitation process assisted by grain boundary sliding. The current study showed that the β‐ →α‐phase transformation had little effect on texture development in SiC. Hot forging generally produced the strongest texture, with the calculated maximum of 2.2 times random in samples started with pure α‐SiC phase. The mechanism for texture development was explained based on the microstructural observations.