Abstract

The entrainment of surface oxide films in the melt leads to the formation of double oxide defects in the casting parts. Oxide/metal/oxide (OMO) sandwich technique is a method for physical simulation of the formation of surface oxide film. In this method, air bubbles are artificially introduced into the melt in order to trap two adjacent bubbles and extract the interface between them. In this study, to prepare OMO samples, air bubbles were blown with a pressure of 0.8 atm. into the mold filled with Al melt containing 3, 5 and 7 wt% of Zn. Using scanning electron microscopy and energy-dispersive X-ray spectroscopy, characteristics of dynamically formed oxide films such as morphology and film thickness were investigated. Results showed that in higher zinc content, more cracks appear on the oxide films. Thickness of the oxide films in Al–Zn alloys was estimated to be 95–1070 nm. According to the measurement performed on the folds, adding more than 3% zinc caused a reduction in the oxide film thickness. Thermodynamics suggests the presence of spinel phase along with aluminum oxide at 700 °C which is in agreement with energy-dispersive X-ray spectroscopy’s results. The presence of the spinel phase at the interface is the reason behind the reduction in the thickness of the oxide film.

Graphic Abstract

中文翻译：

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Al-Zn熔体中动态形成的氧化膜的特征

摘要

在熔体中夹带表面氧化物膜导致在铸件中形成双氧化物缺陷。氧化物/金属/氧化物（OMO）夹层技术是一种物理模拟表面氧化物膜形成的方法。在这种方法中，将气泡人工引入熔体中，以捕获两个相邻的气泡并提取它们之间的界面。在这项研究中，为了制备OMO样品，以0.8 atm的压力吹入气泡。倒入装有含3、5和7 wt％的Zn的Al熔体的模具中 使用扫描电子显微镜和能量色散X射线光谱，研究了动态形成的氧化膜的特征，如形态和膜厚。结果表明，在较高的锌含量下，氧化膜上会出现更多的裂纹。Al-Zn合金中氧化膜的厚度估计为95-1070 nm。根据对折痕的测量，添加超过3％的锌导致氧化膜厚度减小。热力学表明在700°C时存在尖晶石相和氧化铝，这与能量色散X射线光谱法的结果一致。界面处尖晶石相的存在是氧化膜厚度减小的原因。

图形摘要