Study for Loading Rate Dependence on Strength Properties of Advanced Pore-Free SiC with Damage Tolerance

Abstract

Advanced Pore Free SiC (APF-SiC) developed by newly improved reaction sintering method has excellent property such as super-high strength and damage tolerance ability by preceding failure of uniformly dispersing residual metallic silicon particles. In order to clarify effects of damage tolerance on strength property of this material, we have researched by carrying out 4-point bending tests at loading rates. As the result, at above loading rate of 0.5mm/min, it is found that the fracture strengths increase slightly with increasing loading rate. It is considered that delay fracture depended on the time from starting of slip of inclusion to fracture occurs in this material. One the other hand, it is found that the fracture strengths also increase at below loading rate of that. Generally, strength of the residual metallic silicones inviting damage tolerance decreases with decreasing loading rate since slow crack growth occurs. Then a lot of internal energy accumulated by loading is released with decreasing loading rate in this material. Therefore it is considered that resistance toward slip of inclusions increases and this behavior causes damage tolerance in this material, where can be theory explained by effects loading time. Moreover, it is suggested that unified strength estimation method proposed by Okabe et al.10) would be effectively to estimates strength property of material with damage tolerance ability.