錳及鋁含量對銅錳鋁合金相變化影響

Abstract

在本論文中，我們利用掃描穿透式電子顯微鏡 (STEM) 和X-光能量散佈分析儀 (EDS) 研究觀察錳以及鋁含量對銅-錳-鋁三元合金顯微結構變化的影響。根據我們的實驗觀察，得到以下幾項結果：: （一）當Cu2MnA1@@@46合金在460℃做時效處理時，板狀的β-錳析出 物在L2,基地中析出、而時效溫度提高至560℃，β-錳的 形狀由板狀變成顆粒狀。由電子繞射實驗可知儘管β-錳 的形狀會隨時效溫度改變，然而β-錳與L21基地間的方向 關係卻仍相同。此方向關係可表示成： (210)β[nn//(100)m,(120)βWMn//(010)m,(001)β/Mn//(001)m 此結果與R.. Kuzobski等學者在Cu2MnA]合金中所觀察到的截然不同。 （二）銅-30錳-25鋁合金在淬火狀態下的顯微結構為 (B2+L2i+L-J) 混合相，其中在L21基地中可發現極細的B2顆粒析出、此合金在300℃至700℃之間做時效處理時所產生的相變 化反應依序為：(B2+L2i)→(B2+L21.β-錳+γ-brass)→(β- 錳+γ-brass)→(β-錳+L21)→(B2+L21+L-J)。在此值得一提 的是β-錳及r-brass共存之現象從未被其他學者在銅- 鋁、銅-錳、及銅-錳-鋁合金系統中觀察到。 （三）由穿透式電子顯微鏡觀察銅-24.8錳-30.0鋁合金的實驗發現此合金在淬火狀態下的顯微結構為 (B2+L21+L-J) 混合相。此合金在350℃至750℃之間做時效處理時所產生的相 變化反應依序為 (B2+L21+L-J)→(B2+γ-brass)→(B2+γ- brass)→(B2+L21+γ-brass+L-J)→(B2+L21+L-J)。在此值得 一提的是在銅-鋁、銅-錳、及銅-錳-鋁合金系統中，從未 發現B2與L21，共存的現象。 （四）銅-25錳-35鋁合金在固溶狀態下的顯微結構為 (B2+L-J) 混合相。當銅-25錳-35鋁合金在350℃至700℃間做時效處理時，僅γ-brass在B2基地中析出。

In the present study, the effects of Mn and Al contents on the phase transformations in the of Cu-Mn-AI ternary alloys have been investigated by means of scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectrometer (EDS). Based on our examinations, some results can be summarized as follows: (1) When Cu2MnAl the alloy was aged at 460℃, the plate-like β-Mn precipitates had occurred within the L21 matrix. As the aging temperature was increased to 560℃, the morphology of the β-Mn precipitates changed from plate-like to granular shape. Electron diffraction examinations indicated that in spite of the morphology change the orientation relationship between the β-Mn and the L21 matrix would still maintain the same, and it could be best stated as follows: (210)β[nn//(100)m,(120)βWMn//(010)m,(001)β/Mn//(001)m This result is in disagreement with that reported by R.Kuzobski et al. in the aged Cu2MnAl alloy. (2) In the as-quenched condition, the microstructure of the Cu-30Mn-25Al alloy revealed a mixture of (B2+L21+L-J) phases, where the extremely fine B2 precipitates were formed within the L21 domains. When the Cu-30Mn-25Al alloy was aged at the temperatures ranging from 300℃ to 700℃, the sequence of the microstructural changes was found to be: (B2+L21)→(B2+L21.β-錳+γ-brass)→(β-錳+γ-brass)→(β-錳+L21) →(B2+L21+L-J). It is worthwhile to mention here that the coexistence of the β-Mn and γ-brass phases has never been observed by other workers in the Cu-Al, Cu-Mn and Cu-Mn-Al alloy systems before. (3) Transmission electron microscopy examinations of the Cu-24.8Mn-30.0Al alloy indicated that the as-quenched microstructure of the alloy was a mixture of (B2+L21+L-J) phases. As the alloy was aged at the temperatures ranging from 350℃ to 750℃, the phase transition sequence of the Cu-24.8Mn-30.0Al alloy was observed to be (B2+L21+L-J)→(B2+ γ-brass)→(B2+γ-brass)→(B2+L21+γ-brass+L-J)→(B2+L21+L-J). It is noted here that the coexistence of the B2 and L21 phases has never been observed by other workers in the as-quenched Cu-Al, Cu-Mn and Cu-Mn-Al alloy systems before. (4) The as-quenched microstructure of the Cu-25Mn-35Al alloy was a mixture of (B2+L-J) phases. When the Cu-25Mn-35Al alloy was aged at the temperatures ranging from 350℃ to 700℃ , only γ-brass precipitates could be found within the B2 matrix.