The effect of Mg on the microstructure and mechanical behavior of Al-Si-Mg casting alloys
The effect of Mg on the microstructure and mechanical behavior of Al-Si-Mg casting alloys
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DOI：
10.1007/s11661-999-0301-8
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发表时间：
1999-10-01
影响因子：
2.8
通讯作者：
Wang, QG
中科院分区：
文献类型：
--
作者：
Caceres, CH;Davidson, CJ;Wang, QG
研究了镁含量分别为0.4%和0.7%的Al-7%Si-Mg铸造合金的显微组织和拉伸行为。通过改变凝固速度和用锶变质处理，可以得到不同的显微组织。用萃取技术确定了共晶硅片和颗粒的最大尺寸。在镁含量较高的合金中，未变质合金中的共晶硅颗粒较大，而锶变质合金中的共晶硅颗粒较少。0.7%的Me合金中形成了大的富Fe的pi相(Al9FeMg3Si5)颗粒和一些较小的β相(Al5FeSi)片状；相反，在0.4%的镁合金中只观察到了β相的片状。屈服应力随着镁含量的增加而增加，但在0.7%的镁含量下，屈服应力比预期的要小，这可能是因为部分镁丢失到了pi相金属间化合物中。与镁含量较低的合金相比，镁含量较高的合金，特别是锶变质合金的拉伸塑性较低。未变质合金的塑性损失似乎是由较大的Si颗粒引起的，而大的pi相金属间化合物颗粒的存在是锶变质合金塑性损失的原因。
The microstructure and tensile behavior of two Al-7 pct Si-Mg casting alloys, with magnesium contents of 0.4 and 0.7 pct, have been studied. Different microstructures were produced by varying the solidification rate and by modification with strontium. An extraction technique was used to determine the maximum size of the eutectic silicon flakes and particles. The eutectic Si particles in the unmodified alloys and, to a lesser extent, in the Sr-modified alloys are larger in the alloys with higher Mg content. Large Fe-rich pi-phase (Al9FeMg3Si5) particles are formed in the 0.7 pct ME alloys together with some smaller beta-phase (Al5FeSi) plates; in contrast, only beta-phase plates are observed in the 0.4 pct Mg alloys. The yield stress increases with the Mg content, although, at 0.7 pct Mg, it is less than expected, possibly because some of the Mg is lost to pi-phase intermetallics. The tensile ductility is less in the higher Mg alloys, especially in the Sr-modified alloys, compared with the lower Mg alloys. The loss of ductility of the unmodified alloy seems to be caused by the larger Si particles, while the presence of large pi-phase intermetallic particles accounts for the loss in ductility of the Sr-modified alloy.