銅合金在含氟環境中的兩種不同的破裂型態

Two Distinct Fracture Modes of Copper Alloys in Fluoride Environments

本研究主要是利用慢速應變拉伸試驗來評估鋁黃銅與鋁青銅在含氟化物環境中，氟化物濃度與外加電位對這兩種銅合金其應力腐蝕破裂敏感性所造成的效應。實驗結果發現：鋁黃銅產生應力腐蝕的機制與去合金現象有關；而鋁青銅發生應力腐蝕的機制則是在某一範圍之外加電位下的鈍化膜剝落。對鋁黃銅來說，應力比與破裂時間比與氟離子濃度的對數值有很密切的關係。而鋁黃銅在其腐蝕電位的破裂型態是屬於延性撕裂狀的窩穴；另一方面，鋁青銅在過鈍態電位以上的破裂形式則是沿晶破裂。最後，本研究使用合金組成元素的微伽凡尼效應來估計兩種銅合金的陽極平衡電位。

The susceptibility of aluminum brass and aluminum bronze to stress corrosion cracking (SCC) was evaluated in fluoride environments by means of the slow strain rate technique. The effects of fluoride concentration and applied electrochemical potential on the SCC susceptibility were investigated. The SCC mechanism of aluminum brass was found to be dependent upon the de-alloying phenomenon while that of aluminum bronze on the film rupture mechanism occurring within a certain range of applied electrochemical potentials. For aluminum brass, both the stress ratio and the time-to-fracture ratio were closely related to the logarithmic concentration of F- ions. The fracture modes were ductile dimpled tearing fracture for the aluminum brass at the corrosion potential while intergranular for the aluminum bronze at various anodic potentials. The microgalvanic effects of the constituent elements were used to estimate the anodic equilibrium potentials of the two alloys.