多元高熵合金及2205雙相不銹鋼在鋁湯中之固液界面反應比較研究

A Comparative Study on Interfacial Reactions Involving Molten Aluminum in Contact with a Multicomponent FeCrNiCoMnAl High Entropy Alloy and a 2205 Duplex Stainless Steel

本研究利用XRD、SEM以及EDS等分析方法，從相組成、微觀結構、化學成分的角度，對具有雙相組織的FeCrNiCoMnAl高熵合金及2205雙相不銹鋼與鋁湯接觸時之界面反應加以探討。研究結果顯示，在FeCrNiCoMnAl高熵合金中，BCC相中含有較高濃度的鎳，FCC相則具有較高濃度的鉻，其組成相的穩定元素與2205雙相不銹鋼相反。在700℃之鋁湯中浸泡一小時，高熵合金與鋁湯的界面出現FCC結構的奈米晶薄層；隨著浸泡時間的增加，此界面層之結晶性增加且厚度增厚。至於2205雙相不銹鋼與鋁湯的界面則產生明顯的θ-FeAl3介金屬層，隨著浸泡時間的增加，界面反應產物轉變成內η-Fe2Al5及外θ-FeAl3的雙層結構。實驗的結果亦顯示，FeCrNiCoMnAl高熵合金在鋁湯中的溶解反應速率比2205雙相不銹鋼為慢。

A multicomponent FeCrNiCoMnAl High Entropy Alloy (HEA) and a 2205 duplex stainless steel (DSS) were immersed in molten Al at 700° C for various periods of time, and the respective interfacial reactions were investigated. Material characterization on two solid phases showed that the BCC phase in the FeCrNiCoMnAl HEA was rich in Ni and Al elements while the FCC phase in this HEA was rich in Fe and Cr elements. These elemental enrichment results were in contrary to those in the dual phases of the 2205 DSS. After immersion of the HEA in a 700 ℃ Al melt for 1 h, a continuous thin layer consisting of a nanocrystalline FCC phase was found in the HEA/Al interface. The crystallinity of the reaction product increased with prolonged immersion time, accompanying with increasingly thickening interlayer. In contrast, a thicker FeAl3 intermetallic layer was formed in the DSS/Al interface. This layer further developed into a complex structure consisting of an inner Fe2Al5 and an outer FeAl3 layers. Finally, the metal loss rate of the FeCrNiCoMnAl HEA in molten Al was slower than that of the 2205 DSS.