σ相的析出對AISI 309L不銹鋼耐局部腐蝕性的影響

Effect of σ Phase Precipitation on the Localized Corrosion Resistance of AISI 309L Stainless Steels

本研究群在σ相的析出動力學已經提出初步的研究結果，由定量金相與δ-肥粒鐵含量的量測結果，發現δ-肥粒鐵轉變為σ相的動力學模式遵循Johnson-Mehl方程式，不銹鋼的性質也因為此種共析分解反應的發生而改變。本研究利用10%草酸電解腐蝕試驗、65%沸騰硝酸腐蝕試驗、雙環動電化學再活性試驗、6%氯化亞鐵試驗、拉伸試驗與硬度量測探討σ相對AISI 309L不銹鋼耐局部腐蝕性與機械性質的影響。本文結合前篇所提出之析出動力學模式，含量在高溫環境下促進不銹鋼δ-肥粒鐵相的分解與σ相析出的行為，以及相變化對材料耐局部腐蝕性與機械性質的影響作一完整的論述。

Silicon adopted stainless steels can be characterized by the existence of δ-ferrite and its phase transformation into σ phase. The precipitation kinetics of σ phase was studied. It was proved that the precipitation of σ phase follows the Johnson-Mehl equation in the previous study of our research group. 10 oxalic acid test, 65 boiling nitric acid test, DLEPR test and 6 ferrite chloride test, tensile test and hardness test were performed to investigate the effect of σ phase precipitation on the localized corrosion resistance of AISI 309L stainless steels. The influence of silicon content on the behavior of δ-ferrite decomposition and σ phase precipitation in stainless steel was discussed in this paper. These results were combined with the kinetic precipitation model that was referred before and the decomposition of δ-ferrite and the precipitation of σ phase. The effect of this phase transformation on the localized corrosion resistance and mechanical properties was quantitatively studied also.