1991 Volume 99 Issue 1153 Pages 809-812
The relation between grain morphology and mechanical properties has been extensively studied. Although mechanical properties are related to the real three-dimensional forms of grains, the real three-dimensional form can not be observed. Grains through a cross section can only be observed. The difference between the real three-dimensional and cross sectional form is large especially in rod-like grains. In this report, the aspect ratio of rod-like grains, which have a great influence on the mechanical properties, was studied. A relationship between the real three-dimensional aspect ratio (=A) and the cross sectional aspect ratio (=AR) was derived from model calculation; AR=-ln{cos(tan-1A)}+A(π/2-tan-1A). The model ueed assumed that the grains were rod-like, of uniform length and orientated randomly. The corresponding cross sectional aspect ratios were calculated to be 2.1, 2.6, 3.3, 4.0 for the real three-dimensional aspect ratios of 3, 5, 10 and 20. When the real aspect ratio is large, the difference between the real and cross sectional aspect ratios is also large. The calculated results were compared with the experimental data for a 20wt% SiC whisker-Si3N4 pressureless sintered body. Close agreement between calculated and experimental results was obtained.
