銅鋁鎳合金之相變化

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)研究觀察鎳含量對銅-鋁-鎳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] 在淬火狀態下，Cu-14.6wt.%Al-4.3wt.%Ni合金的淬火顯微結構為D03相的基地和極微細的析出物。根據實驗結果顯示，此微細析出物為L-J相，並非2H相。此外，由電子顯微鏡繞射分析顯示，L-J相會在D03基地中以兩個variants產生。此結果與其他學者在Cu-14.2Al-4.3Ni合金中所現的結果不同。 [二]在淬火狀態下，Cu-14.2wt.%Al-4.3wt.%Ni、Cu-14.2wt.%Al-6.0wt.%Ni及Cu-14.2wt.%Al-10.0wt.%Ni合金的淬火顯微結構皆為(D03+L-J)相。其中，L-J相的含量會隨著Ni含量的增加而增加。相反地，D03 domain size卻會隨著Ni含量的增加而減小。另外，在Cu-14.2wt.%Al-4.3wt.%Ni及Cu-14.2wt.%Al-6.0wt.%Ni合金中並無法觀察到a/4<111>反相晶界，而卻能在Cu-14.2wt.%Al-10.0wt.%Ni合金中清楚地觀察到a/4<111>反相晶界，此一實驗結果從未在銅-鋁-鎳三元合金中被其他學者發現過。 [三] 根據實驗結果，Cu-14.2wt.%Al-6.0wt.%Ni及Cu-14.2wt.%Al-10.0 wt.%Ni合金在300°C至750°C之間時效處理時產生的相變化反應分別為(D03+L-J+g2) ® (B2+L-J+g2) ® (B2+2H martensite+L-J+g2) ® (B2+disordered b+g2) ® (a+g2) ® (B2+g2) ® b及(D03+L-J+g2) ® (B2+L-J+g2) ® (g2+B2*+disordered b) ® b。在此值得一提的是較高的鎳含量在銅鋁鎳合金中使得B2 ® D03的相變化溫度降低。

In the present study, the effects of nickel content on the microstructural changes of Cu-Al-Ni 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] In the as-quenched condition, the microstructure of the Cu-14.6Al-4.3Ni alloy was D03 phase containing extremely fine precipitates. Transmission electron microscopy examinations indicated that the extremely fine precipitates should belong to the L-J phase, rather than 2H phase. In addition, electron diffraction analyses indicated that the L-J precipitate has two variants with the D03 matrix. These results are quite different from those reported by other workers in a Cu-14.2Al-4.3Ni alloy. [2] The microstructures of the Cu-14.2wt.%Al-4.3wt.%Ni, Cu-14.2wt.%Al-6.0wt.%Ni and Cu-14.2wt.%Al-10.0wt.%Ni alloys was D03 phase containing extremely fine particles. The extremely fine particles should belong to the L-J phase, rather than 2H phase. The amount of the L-J particles was decreased with increasing the nickel content. On the contrary, the size of the D03 domains was decreased with increasing the nickel content. No evidence of the a/4 <111> APBs could be detected in the both alloy A and alloy B. However, the a/4<111> APBs were clearly observed in the alloy C. This result has never been reported by other workers in the Cu-Al-Ni ternary alloys before. [3] Transmission electron microscopy examinations indicated that when the as-quenched Cu-14.2wt.%Al-6.0wt.%Ni alloy was aged at temperatures ranging from 300°C to 750°C, a (D03+L-J+g2) ® (B2+L-J+g2) ® (B2+2H martensite+L-J+g2) ® (B2+disordered b+g2) ® (a+g2) ® (B2+g2) ® b phase transition occurred; whereas, when the as-quenched Cu-14.2wt.%Al-10.0wt.%Ni alloy was aged at temperatures ranging from 300°C to 700°C, a (D03+L-J+g2) ® (B2+L-J+g2) ® (B2*+disordered b+g2) ® b phase transition occurred. The addition of higher nickel content to the Cu-Al-Ni alloy would lower the B2 ® D03 transition temperature.