Crack propagation characteristics and fracture surface energy of boride cermets

Hiromoto Kitahara, Yasuhiro Yoshikawa, Fuyuki Yoshida, Hideharu Nakashima, Kazuo Hamashima, Yasuo Shinozaki, Hiroshi Abe

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


The present study was carried out to clarify the relationship between the microstructures and mechanical properties of Mo2NiB2-Zvol%Ni (Z = 0, 12, 18, 24 and 50). Fracture surface energy, γi, for crack initiation and work of fracture surface energy, γwof, for crack propagation were selected as suitable parameters for evaluating the mechanical properties. γi and γwof were measured by the Chevron notch three-point bend methods. Both γi and γwof increased with the increase in amount of metal phase in cermets, and γwof were about two or three times higher than γi for all specimens. Both γi and γwof did not increase proportionally to the volume fraction of cermets. In order to clarify that microstructure affected crack propagation, crack propagation patterns were classified to four patterns; transgranular fracture in ceramics (c), intergranular fracture in ceramics (c/c), transgranular fracture in metal (m) and intergranular fracture between metal and ceramics (m/c). The intergranular fracture (c/c) ratio to total crack propagation patterns was large in 0, 12, 18 and 24 vol% cermets, and intergranular fracture (m/c) ratio was large in 50 vol% cermet. Increase in the volume fraction of metal was rearranged as the frequency of cracks to touch metal phase; m + 0.5 (m/c). Linear relationship was obtained between m + 0.5 (m/c) and fracture surface energies. The result of fracture surface analysis showed that the large increase in γwof compared with γi with the increase in the volume fraction of metal resulted from the difference of the roughness of fracture surfaces. The fracture surfaces were rougher for the specimens with larger amount of metal phase. γwof was estimated to be about equal to γi when correction was carried out based on the roughness value. It was concluded that fracture surface energies γi and γwof increased proportionally to the fraction of the metal phase which was contiguous to crack.

Original languageEnglish
Pages (from-to)1116-1121
Number of pages6
JournalNippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
Issue number11
Publication statusPublished - Nov 2002

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys
  • Materials Chemistry


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