銅-19.5錳-12.8鋁合金相變化

Abstract

中文摘要 在本論文中，我們利用穿透式電子顯微鏡(STEM)、X-ray能量散布分析儀(EDS) 研究Cu-19.5Mn-12.8Al 合金之相變化。發現在淬火的情況下，其顯微結構為(D03+L21+L-J)相的混合，從電子顯微鏡觀察的結果發現到L-J的相會在(D03+L21)基地中以兩個variants產生；其顯微結構為orthorhombic，其晶格常數為a=0.413nm, b=0.254nm 和c=0.728nm。 當合金在300℃溫度作時效處理後，此合金的顯微結構仍為(D03+L21+L-J)的相。然而，當時效溫度提高到350℃或450℃，則γ-brass 相會在a/2<100>的反向晶界上和基地內析出。當溫度提高到550℃作時效處理後，會發現到β-Mn在粗的γ-brass相旁邊開始析出。當時效處理溫度增加到650℃後，合金的顯微結構變為(B2+L-J+β-Mn)的混合相。最後，當時效溫度升高至750℃或以上時，合金之顯微結構與淬火狀態相同，亦為(D03+L21+L-J)相的混合。 從實驗的結果，我們可以歸納出此成份合金從300℃到750℃的一系列相變化過程：(D03+L21+L-J)→(D03+L21+L-J+γ-Cu9Al4)→(L21(D03)+L-J+γ-Cu9Al4)→(L21(D03)+L-J+γ-Cu9Al4+b-Mn)→(B2+L-J+b-Mn)→disordered b phase.

Abstract Phase transformations in the Cu-19.5Mn-12.8Al alloy have been studied by using energy dispersive x-ray spectrometer (EDS) and scanning transmission electron microscopy (STEM) . In the as-quenched condition, the microstructure of the alloy was the mixture of (D03+L21+L-J) phases. Transmission electron microscopy examinations indicated that the L-J phase was formed within the matrix with two variants. The L-J phase has an orthorhombic structure with lattice parameters a=0.413nm, b=0.254nm and c=0.728nm. When the Cu-19.5Mn-12.8Al alloy was aged at 300℃ or below, the microstructure of the alloy was still (D03+L21+L-J) phases. However, when aging temperature was increased to 350℃ or 450℃, it was found that the γ-brass precipitates started to appear on the a/2<100>-type anti-phase boundaries and within the D03 domains. With increasing the aging temperature up to 550℃, the β-Mn particles were found to appear at the regions contiguous to the coarse γ-brass precipitates. When the aging temperature was increased to 650℃, the microstructure of the alloy was the mixture of (B2+L-J+β-Mn) phases. As the aging temperature was increased to 750℃ or above, only (D03+L21+L-J) phases could be found. Based on the above observations, the phase transformation sequence as the aging temperature increased from 200℃ to 750℃ was (D03+L21+L-J)→(D03+L21+L-J+γ-Cu9Al4)→(L21(D03)+L-J+γ-Cu9Al4)→(L21(D03)+L-J+γ-Cu9Al4+b-Mn)→(B2+L-J+b-Mn)→disordered b phase.