Premium
MORPHOLOGICAL STUDIES RELATING TO THE FRACTURE STRESS AND FRACTURE TOUGHNESS OF SILICON NITRIDE
Author(s) -
Chu M. C.,
Sato S.,
Kobayashi Y.,
Ando K.
Publication year - 1997
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/j.1460-2695.1997.tb01527.x
Subject(s) - fracture toughness , materials science , microstructure , flexural strength , composite material , silicon nitride , indentation , scanning electron microscope , fracture (geology) , bending , grain size , layer (electronics)
— Microstructure and mechanical properties of HP (Hot Pressed), HP/GP (Gas Pressed), and HP/HIP (Hot Isostatic Pressed)—Si 3 N 4 are studied using scanning electron microscopy, bending tests and the indentation fracture method. The grain diameter distribution is analyzed to clarify the relationship between microstructure and mechanical properties; and also the bending strength and fracture toughness. It is shown that bending strength increases with decreasing grain diameter. The results also show that a Hall—Petch type of relationship is obtained between grain diameter and fracture strength. The fracture toughness shows a linear relationship with , where σ F = bending strength, β= a proportionality factor and d a = average grain diameter, and is closely related to the aspect ratio of Si 3 N 4 grains. It is concluded, from the morphological analysis, that a microstructure composed of Si 3 N 4 grains, with both a small grain diameter and a large aspect ratio, is effective in improving both the fracture strength and fracture toughness.