In this work, Mo was added into Al melt to reduce the detrimental effect of double-oxide film defect. An air bubble was trapped in a liquid metal (2L99), served as an analogy for double-oxide film defect in aluminum alloy castings. It was found that the addition of Mo significantly accelerated the consumption of the entrapped bubble by 60 pct after holding for 1 hour. 2 sets of testbar molds were then cast, with 2L99 and 2L99+Mo alloy, with a badly designed running system, intended to deliberately introduce double oxide film defects into the liquid metal. Tensile testing showed that, with the addition of Mo, the Weibull modulus of the Ultimate Tensile Strength and pct Elongation was increased by a factor of 2.5 (from 9 to 23) and 2 (from 2.5 to 4.5), respectively. The fracture surface of 2L99+Mo alloy testbars revealed areas of nitrides contained within bi-film defects. Cross-sections through those defects by Focused Ion Beam milling suggested that the surface layer were permeable, which could be as thick as 30 μm, compared to around 500 nm for the typical oxide film thickness. Transmission Electron Microscopy analysis suggested that the nitride-containing layer consisted of nitride particles as well as spinel phase of various form. The hypothesis was raised that the permeability of the nitride layers promote the reaction between the entrapped atmosphere in the defect and the surrounding liquid metal, reducing the defect size and decreasing their impact on mechanical properties.

中文翻译：

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在Al-Si-Mg合金中添加Mo对双氧化膜缺陷的改性

在这项工作中，将钼添加到铝熔体中以减少双氧化膜缺陷的不利影响。气泡被困在液态金属（2L99）中，作为铝合金铸件中双氧化膜缺陷的类比。发现Mo的添加在保持1小时后显着加速了夹带气泡的消耗60%。然后铸造了 2 套测试棒模具，采用 2L99 和 2L99+Mo 合金，运行系统设计不当，旨在故意将双氧化膜缺陷引入液态金属。拉伸测试表明，添加 Mo 后，极限拉伸强度和 pct 伸长率的威布尔模量分别增加了 2.5 倍（从 9 到 23）和 2 倍（从 2.5 到 4.5）。2L99+Mo 合金测试棒的断口表面显示出双膜缺陷中包含的氮化物区域。通过聚焦离子束铣削穿过这些缺陷的横截面表明，表面层是可渗透的，其厚度可达 30 μm，而典型的氧化膜厚度约为 500 nm。透射电子显微镜分析表明，含氮化物层由氮化物颗粒以及各种形式的尖晶石相组成。提出的假设是，氮化物层的渗透性促进了缺陷中夹带的气氛与周围液态金属之间的反应，从而减小了缺陷尺寸并降低了它们对机械性能的影响。通过聚焦离子束铣削穿过这些缺陷的横截面表明，表面层是可渗透的，其厚度可达 30 μm，而典型的氧化膜厚度约为 500 nm。透射电子显微镜分析表明，含氮化物层由氮化物颗粒以及各种形式的尖晶石相组成。提出的假设是，氮化物层的渗透性促进了缺陷中夹带的气氛与周围液态金属之间的反应，从而减小了缺陷尺寸并降低了它们对机械性能的影响。通过聚焦离子束铣削穿过这些缺陷的横截面表明，表面层是可渗透的，其厚度可达 30 μm，而典型的氧化膜厚度约为 500 nm。透射电子显微镜分析表明，含氮化物层由氮化物颗粒以及各种形式的尖晶石相组成。提出的假设是，氮化物层的渗透性促进了缺陷中夹带的气氛与周围液态金属之间的反应，从而减小了缺陷尺寸并降低了它们对机械性能的影响。透射电子显微镜分析表明，含氮化物层由氮化物颗粒以及各种形式的尖晶石相组成。提出的假设是，氮化物层的渗透性促进了缺陷中夹带的气氛与周围液态金属之间的反应，从而减小了缺陷尺寸并降低了它们对机械性能的影响。透射电子显微镜分析表明，含氮化物层由氮化物颗粒以及各种形式的尖晶石相组成。提出的假设是，氮化物层的渗透性促进了缺陷中夹带的气氛与周围液态金属之间的反应，从而减小了缺陷尺寸并降低了它们对机械性能的影响。