摘要
通过X射线衍射、扫描电镜等方法分析了变质元素对A356铝合金表面氧化膜成分及形貌的影响。从添加元素对表面氧化膜致密性、完整性的影响角度出发,考察了Al-10RE中间合金、Sr处理对A356合金熔体氢含量的影响机制。试验结果表明:A356合金经过Al-10RE中间合金处理后,表面氧化膜中形成了大量La2O3与Al2O3的复合氧化物LaAl11O18,这种复合氧化物使表面氧化膜更加致密,氧化膜表面非常平整,几乎看不到开裂的现象,有效地阻止了铝与水的反应。而加入Sr后,形成了SrO与Al2O3的复合氧化物SrAl2O4,这种复合氧化物使表面氧化膜致密性变差,氧化膜表面出现大量反复开裂的痕迹,使得新鲜的铝液不断的暴露于空气中,大大促进了铝与水的反应,使熔体氢含量大幅度增加。
The effect of RE-modification and Sr-modification on the surface oxide film of A356 aluminum alloy melt was investigated in this paper. The hydrogen content of the melt was measured by Reduce Pressure Test, and the surface oxide film was achieved using a self-designed device, then the phases in the oxide film were analyzed by X-ray diffraction （XRD） and the morphology of the surface oxide film was observed by Scanning Electronic Microscopy （SEM）. It had been found that RE-modification reduced the hydrogen content of A356 aluminum alloy and Sr-modification increased the hydrogen content remarkably. XRD results showed that, after treated with RE, a large number of LaAl11O18, which consists of Al2O3 and La2O3, was generate in the surface oxide film. This compound oxide makes the surface film compacter and restrains water react with aluminum, so reduce the hydrogen content of the melt. And after treated with Sr, the surface oxide film was almost composed of Al2SrO4, but this compound oxide makes the surface oxide film looser. According to the results of SEM, the surface oxide film of Sr-modification was easier to crack than that of RE-modification, which accelerate the vapour diffusing into the melt, consequently, increase the tendency of porosity formation in A356 alloy melt significantly.
出处
《铸造》
CAS
CSCD
北大核心
2006年第10期1071-1074,共4页
Foundry
