用TGA、OM、SEM和HREM等方法研究了Cu含量不同的几种AgCu合金在750℃及850℃的内氧化行为。发现氧化12h后,Ag-0.8at％Cu合金中的Cu已完全以CuO颗粒析出;含有3.3和6.3at％Cu的合金还没有完全被内氧化;这三种样品表面析出较均匀的CuO颗粒,而Cu含量过高(≥9.5at％)时的合金表面形成含有大量CuO颗粒簇的隆起物。从内氧化层的截面形貌看,750℃下的Ag-0.8at％Cu、Ag-3.3at％Cu,850℃下Ag-0.8at％Cu合金内氧化时单位体积内析出的CuO颗粒密度随内氧化深度增加而降低,而其它试验条件下没有类似变化。通过对内氧化AgCu合金的原子结构进行观察,发现其中存在一定密度的空位型堆垛层错四面体(SFT),认为这些SFT是氧化过程中由“Kirkendall”空位聚集形成的空位型层错。它在内氧化前沿产生,促进了Cu的扩散以及CuO的形核。提出了导致内氧化物在合金内氧化层均匀析出的途径。
The internal oxidation behavior of AgCu alloys with various Cu contents at 750℃ and 850℃ was studied by means of TGA, OM, SEM and HREM. After 12h oxidation of the alloys, it was found that, all Cu was precipitated as CuO particles for Ag-0.8at%Cu but not for Ag-3.3at%Cu and Ag-6.3at%Cu alloys, and CuO particles were precipitated homogeneously in the surface of samples of the above three alloys. The exception was the alloys with Cu contents more than 9.5%, in the surface of which appeared some protrusions containing a great deal of CuO particle clusters. The metallograph of cross sections of internally oxidized samples showed that the nucleation and growth of CuO precipitation varied with the Cu contents. The number of CuO particles precipitated per unit volume decreased with the advance of internal oxidation for Ag-0.8at%Cu, Ag-3.3at%Cu at 750℃ and Ag-0.8at%Cu at 850℃ but not for the other alloys. A certain degree of Stacking Fault Tetrahedron (SFT), which was believed to be a vacancy-type fault formed by the "Kirkendall" vacancies created during internal oxidation process was observed in alloys by HREM at atomic level. It was believed that the SFT produced in internal oxidation front might promote the diffusion of Cu as the nucleation for CuO precipitation. Meanwhile, methods for homogeneous precipitation of CuO particles in internally oxidized AgCu alloys were proposed.
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