錳含量對銅錳鋁合金相變化之影響

Abstract

本論文利用光學顯微鏡，掃描穿透式電子顯微鏡和X光能量散佈分析儀等，研究觀察不同之錳含量對銅-錳-鋁三元合金顯微結構組織的影響。 本論文所得到的具體研究結果如下:

(一)、在淬火狀態下，Cu2.9Mn0.1Al(Cu-2.7at.%Mn-25.1at.%Al)合金顯微結構為D03相與淬火過程中經由麻田散相變化轉變成γ1΄麻田散相之混合相。然而我們發現在淬火狀態下，Cu2.8Mn0.2Al(Cu-5.1 at.%Mn-25.3at.%Al)與Cu2.7Mn0.3Al(Cu-7.6at.%Mn-25.1at.%Al)合金，其顯微結構為D03相和極細微之L-J混合相。但是在Cu2.6Mn0.4Al(Cu-10.3at.%Mn-25.2at.%Al)合金在淬火狀態下之顯微結構則變成為D03、L21與L-J之混合相，此結果與先前Bouchard等其他學者在銅-錳-鋁三元合金系統中所發現到的結果不同。在本研究中我們可清楚的觀察到a/4<111 >反向晶界存在於Cu2.9Mn0.1Al、Cu2.8Mn0.2Al及Cu2.7Mn0.3Al合金中，這是一個強而有力的直接證據證明D03相是經由β→B2→D03連續規律化變態所形成的。此處特別值得一提的是，至今a/4<111>反向晶界從未被其他學者在銅-錳-鋁合金系統中發現過。

(二)、當Cu2.7Mn0.3Al (銅-7.6at.%錳-25.1at.%鋁)合金在固溶處理後急速淬火後，其顯微結構為D03和極細微之L-J混合相，其中D03相是在淬火過程中經由β→B2→D03連續規律化變態所形成的。當此合金在500℃做適當時間之時效處理後，γ-brass相會開始在D03 基地中沿著a/2<100>反向晶界析出。然而，隨著時效時間的增加，L-J析出物開始在γ-brass顆粒周圍的鄰近區域析出，此γ-brass與L-J的共存現象至今從未被其他學者在銅-錳-鋁合金系統中發現過。此合金在500℃至700℃溫度範圍內做時效處理後其顯微結構之變化依序為：(γ-brass+L-J+D03)→(γ-brass+L-J+B2)→β。此結果與其他學者在Cu3-xMnxAl三元合金中當X<0.32時所發現到的結果截然不同。

(三)、在淬火狀態下，Cu1.6Mn1.4Al (銅-35.1at.%錳-25.1at.%鋁)合金的淬火顯微結構為L21、B2與L-J之混合相，這個發現和其他學者在Cu3-xMnxAl合金（X<1.0）合金中所發現到的結果不同。當此合金在460℃做短時間時效處理後，γ-brass顆粒會開始在L21基地中沿著反向晶界析出。隨著時效時間的增加，γ-brass析出物逐漸成長並且β-Mn析出物開始在γ-brass析出物之周圍析出，γ-brass與β-Mn之間的方向關係為(001)γ-brass//(012)β-Mn and (011)γ-brass// (031)β-Mn ，此γ-brass與β-Mn的共存現象至今從未被其他學者在銅-錳-鋁合金系統中發現過。此合金在460℃至700℃溫度範圍內做時效處理後其顯微結構之變化依序為：(γ-brass+β-Mn)→(β-Mn+B2) →β。

Effects of the manganese (Mn) content on the phase transformations of the Cu-Mn-Al ternary alloys have been investigated by means of optical microscopy, scanning transmission electron microscopy and energy- dispersive X-ray spectrometry. On the basis of the experimental examinations, several results can be summarized as follows:

[1].We have studied the Cu3-xMnxAl alloy systems at room temperature. In the as-quenched condition, the microstructure of the Cu2.9Mn0.1Al (Cu-2.7 at.%Mn-25.1at.%Al) alloy was a mixture of (D03 + γ1΄ martensite) phases. However, the as-quenched microstructures of the Cu2.8Mn0.2Al (Cu- 5.1at.%Mn-25.3at.%Al) and Cu2.7Mn0.3Al (Cu-7.6at.%Mn-25.1at.%Al) alloys were found to be D03 phase containing extremely fine L-J precipitates. However, as the X increasing to 0.4, that is Cu2.6Mn0.4Al (Cu-10.3at.%Mn-25.2at.%Al) alloy, it was a mixture of (D03 + L21 + L-J) phases in the as-quenched condition. These results are different from those proposed by Bouchard et al. The D03 phase in the Cu2.9Mn0.1Al, Cu2.8Mn0.2Al and Cu2.7Mn0.3Al alloys was formed by a β→B2→D03 continuous ordering transition during quenching, because of the presence of a/4<111> anti-phase boundaries (APBs). It is a strong evidence to demonstrate that the existing D03 phase was formed by a β→B2→D03 continuous ordering transition during quenching. It is worthwhile to note here also that the a/4<111> APBs have never been found in the Cu-Mn-Al alloy systems before.

[2].The as-quenched microstructure of the Cu2.7Mn0.3Al (Cu-7.6at.%Mn- 25.1at.%Al) alloy was D03 phase containing extremely fine L-J precipitates, where the D03 phase existing was formed by a β→B2→D03 continuous ordering transition during quenching. When the as-quenched alloy was aged at 500℃ for moderate times, the γ-brass particles were found to nuclear preferentially at a/2<100> APBs. However, with increasing the aged times at 500℃, the L-J precipitates started to appear at the regions contiguous to the γ-brass particles. The coexistence of (γ-brass+L-J) phases has never been observed by other workers in the Cu-Mn-Al alloy systems before. As the aging temperature was increased from 500℃ to 700℃, the phase transition sequence was found to be (γ-brass+L-J+D03)→(γ-brass+L-J+B2)→β. This result is different from that reported by previous workers in Cu3-xMnxAl alloys with X<0.32.

[3].In the as-quenched condition, the microstructure of the Cu1.6Mn1.4Al (Cu-35.1at.%Mn-25.1at.%Al) alloy was a mixture of (L21+B2+L-J) phases. This is different from that observed by previous workers in the Cu3-xMnxAl alloys with X<1.0. When the as-quenched alloy was aged at 460℃ for short times, γ-brass precipitates started to occur at APBs. After prolonged aging time at 460℃, the γ-brass precipitates grew and β-Mn precipitates generated at the regions contiguous to the γ-brass precipitates. The orientation relationship between the γ-brass and β-Mn was (001)γ-brass//(012)β-Mn and (011)γ-brass//(031)β-Mn. The coexistence of (γ-brass+β-Mn) has never been observed by previous workers in Cu-Mn-Al alloy systems before. When the as-quenched alloy was aged at temperatures ranging from 460℃ to 700℃, the phase transition sequence was found to be (γ-brass+β-Mn)→(β-Mn+L21)→β.