Si含量對AISI 309L不銹鋼σ相析出行為之影響

Effect of Silicon Content on the σ Phase Precipitation of AISI 309L Austenitic Stainless Steels

本研究主要探討Si含量對AISI 309L不銹鋼中σ相的析出與熱處理之關係。根據結果顯示，Si在不銹鋼於800℃進行熱處理的過程中扮演兩種角色，在固溶化的過程中，Si是δ-肥粒鐵的安定元素，可以抑止δ-肥粒鐵分解成為沃斯田鐵。但是在σ相析出的溫度範圍區間，Si則會加速δ-肥粒鐵分解成為σ相，且增加過渡相σ，的析出量，造成不銹鋼中σ相含量的急遽增加，影響不銹鋼的耐晶界腐蝕性。

The purpose of this study is to discuss the effect of silicon content on the precipitation of σ phase in AISI 309L austenitic stainless steels by different aging time. The results evidenced that silicon plays two roles when test materials were thermal treated at 800℃. Silicon stabilized δ-ferrite and restricted the transformation of δ-ferrite into austenite by solution treatment. In the precipitation temperature range of σ phase, silicon accelerated the decomposition rate of δ-ferrite, so that the transformed intermediated phase σ，. This phenomenon promoted the precipitation content of σ phase, and decreased the intergranular corrosion resistance of stainless steels.