鉄系焼結材のヤング率に及ぼす気孔率と気孔形状の影響

抄録

The pore shape in various sintered iron compacts has been found to affect the Young's modulus measured by the resonance method. The Young's moduli of sintered iron and steel compacts are, therefore, discussed in this paper, taking the pore structure into account.
The Young's moduli of sintered steel compacts are not much affected by either the addition of graphite, copper and nickel, or the change of matrix structure due to the heat treatments, but are affected mostly by the pore structures depending upon the types of iron powder.
The value of Young's modulus of commercial sintered iron is lower than that of carbonyl sintered iron which satisfies the equation proposed by Mackenzie; E/E₀≅1-2ε, where E is Young's modulus of sintered iron or steel, E₀ that of bulk material, and ε the porosity. This lowering of the Young's modulus is attributed to the difference in pore shape. Using proposed empirical constants a, b which express some character of the pore shape, the relation between Young's modulus and the porosity can in general be expressed as E/E₀= b/a+ε(1-2ε). The change of Young's modulus for various iron powder materials used can be clearly explained by this equation. The value of a which is determined to be from 0.4 to 0.7 in the experiment takes a larger value as the pore shape becomes spherical. Actual values of a and bare related as b=1.1a.