Effect of strontium and phosphorus on eutectic Al-Si nucleation and formation of β-Al5FeSi in hypoeutectic Al-Si foundry alloys
Effect of strontium and phosphorus on eutectic Al-Si nucleation and formation of β-Al5FeSi in hypoeutectic Al-Si foundry alloys
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DOI：
10.1007/s11661-008-9580-8
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发表时间：
2008-10-01
影响因子：
2.8
通讯作者：
Dahle, A. K.
中科院分区：
文献类型：
--
作者：
Cho, Y. H.;Lee, H. -C.;Dahle, A. K.
研究了含铁0.5和1.1wt%，锶含量在30~500ppm范围内的亚共晶Al-Si合金。当锶的加入量超过100ppm时，共晶数量明显减少，并形成了多边形的Al2Si2Sr金属间化合物。透射电子显微镜研究表明，富P颗粒周围为Al2Si2sr相。这可能表明，Al-Si共晶的强核--磷化铝(AlP)，由于颗粒周围Al2Si2Sr相的形成而中毒或失活。在高铁水平(1.1wtptFe)，预共晶形成的β-Al5FeSi晶片进一步减少了共晶Al-Si形核事件的数量。结果表明，共晶硅和β-Al5FeSi优先在AlP颗粒上形核。因此，在形成Al2Si2Sr或β-Al5FeSi之前，共晶硅的形核变得更加困难，因为可用于形核的硅核较少。在合金中添加高达60ppm的P提高了β-Al5FeSi晶片的形成温度，但没有显著改变晶片的大小，而添加锶则通过降低AlP颗粒的效力而降低了β-Al5FeSi的形核温度。
The present investigation was carried out on hypoeutectic Al-Si alloys containing two levels of Fe, 0.5 and 1.1 wt pct, and Sr in the range of 30 to 500 ppm. The addition of Sr in excess of 100 ppm significantly reduced the number of eutectic grains and also resulted in the formation of polygonal-shaped Al2Si2Sr intermetallics. Transmission electron microscopy studies revealed that the Al2Si2Sr phase surrounded the P-rich particles. This may suggest that the otherwise potent nuclei for the Al-Si eutectic, aluminum phosphide (AlP), become poisoned or deactivated by the formation of the Al2Si2Sr phase around the particles. At the high-Fe level (1.1 wt pct Fe), pre-eutectic formation of beta-Al5FeSi platelets further reduced the number of eutectic Al-Si nucleation events. It is proposed that both eutectic silicon and beta-Al5FeSi are preferentially nucleated on AlP particles. Nucleation of eutectic silicon, therefore, becomes more difficult when it is preceded by the formation of Al2Si2Sr or beta-Al5FeSi, because fewer nuclei are available to nucleate silicon. Addition of up to 60 ppm P to the alloys increased the formation temperature of the beta-Al5FeSi platelets but did not significantly alter the size, whereas the addition of Sr decreased the beta-Al5FeSi nucleation temperature by reducing the potency of the AlP particles.