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Effects of SiC content on the densification, microstructure, and mechanical properties of HfB 2 –SiC composites
Author(s) -
Baharvandi Hamid Reza,
Mashayekh Sadjad
Publication year - 2019
Publication title -
international journal of applied ceramic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 57
eISSN - 1744-7402
pISSN - 1546-542X
DOI - 10.1111/ijac.13323
Subject(s) - materials science , fracture toughness , composite material , microstructure , grain boundary , ultimate tensile strength , residual stress , grain size
To investigate the effects of SiC on microstructure, hardness, and fracture toughness, 0, 10, 20, and 30 vol% SiC were added to HfB 2 and sintered by SPS. Upon adding SiC to 30 vol%, relative density increased about 4%; but HfB 2 grain growth had a minimum at 20 vol% SiC. This may be due to grain boundary silicate glass, responsible for surface oxide wash out, enriched in SiO 2 with higher fraction of SiC. By SiO 2 enrichment, the glass viscosity increased and higher HfO 2 remained unsolved which subsequently lead to higher grain growth. Hardness has increased from about 13 to 15 GPa by SiC introduction with no sensible variation with SiC increase. Residual stress measurements by Rietveld method indicated high levels of tensile residual stresses in the HfB 2 Matrix. Despite the peak residual stress value at 20 vol% SiC, fracture toughness of this sample was the highest (6.43 MPa m 0.5 ) which implied that fracture toughness is mainly a grain size function. Tracking crack trajectory showed a mainly trans‐granular fracture, but grain boundaries imposed a partial deflection on the crack pathway. SiC had a higher percentage in fracture surface images than the cross‐section which implied a weak crack deflection.