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■■■■■■■■■■■■■■■■■■■ 川崎製鉄技報 KAWASAKI STEEL GIHO Vol.1 (1969) No.1 ■■■■■■■■■■■■■■■■■■■ |
| 鉄−低ニッケル合金の降伏について Yield Behavior of Fe-Low Ni Alloys 田中 智夫(Tomoo Tanaka) 渡辺 修司(Shuji Watanabe) |
| 要旨 : 結晶粒径および格子間不純物である炭素の濃度を変化させたFe-1.43％NiおよびFe-3%Ni合金多結晶の降伏応力の温度依存性を調べた。その結果，結晶粒界は各材料の降伏応力の温度依存性に影響を与えず，Fe中のＣ量とNi量が増加すると，降伏応力は室温では高くなり250°Ｋ以下では逆転して低くなること，NiがＣと共存すると，Feの降伏応力へのＣの影響を低下させること，およびNiの添加量が増えること，降伏の活性化エネルギーを減少させることを見出した。実験を検討した結果，降伏応力の温度依存性の機構は，転位と不純物との相互作用による硬化説でも，Niが添加されることによって生ずる剛性率と転位の幅の変化でも説明が困難であることがわかった。 |
| Synopsis : The yield stresses of polycrystalline specimens of iron and Fe alloys (Fe-C, Fe-Ni and Fe-Ni-C) have been investigated in the temperature range between 345°K and 77°K to clarify the effect of nickel on the yield stress of iron. It has been found that Fe-C and Fe-Ni alloys show stronger yield stress than that of iron at room temperature, but that this situation is partly reversed in the temperature range below 250°K, where iron has a higher yield stress. This fact shows that addition of carbon or nickel increases the athermal component of yield stress of iron, and decreases the thermal component. Furthermore, the athermal component depends on the grain size, and the thermal component is independent of the grain size. The yield stress of Fe-3%Ni alloy is unaffected by the addition of carbon, suggesting that the existence of nickel in matrix seems to suppress the effect of carbon on the yield stress. The activation parameters are obtained by means of the strain rate change method, and it has been found that, on increasing the addition of nickel to iron, the activation energy decreases. The analysis of the experimental results has revealed that the temperature dependence of the yield stress can not be fully explained on the basis of the impurity hardening theory by Fleischer or the double kink model by Arsenault. |
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