Mn/Fe摩爾比對A356鑄造鋁合金富鐵相形態(tài)的影響Effects of Mn/Fe mole ratio on iron-rich phase morphology of A356 cast aluminum alloy

在含1.0%Fe(質(zhì)量分數(shù))的A356鋁合金中添加不同含量的Mn，采用OM、SEM、EDS及DSC等分析方法研究Mn/Fe摩爾比對富鐵相形態(tài)的影響及其規(guī)律，探討添加Mn后A356-1.0Fe合金中物相的凝固順序。結(jié)果表明：隨著Mn/Fe摩爾比的提高，富鐵相形態(tài)的演變順序為：針狀→漢字狀→樹枝狀→星形→多邊形狀，當Mn/Fe摩爾比超過1.2時可基本消除針狀鐵相。富鐵相中(Fe，Mn)/Si摩爾比隨富鐵相形態(tài)的凝固先后順序逐漸增加，分別為針狀富鐵相中(Fe，Mn)/Si摩爾比為0.5~0.7，樹枝狀和漢字狀富鐵相中(Fe，Mn)/Si摩爾比為的1.2~1.7，星型和多邊形富鐵相中(Fe，Mn)/Si摩爾比為1.9。富鐵相的平均晶粒尺寸和體積分數(shù)隨Mn/Fe摩爾比的增加先增加后減小，而后再增加。其中當Mn/Fe摩爾比為1.0時，富鐵相的平均晶粒尺寸和體積分數(shù)均為最小，與A356-1.0Fe合金的相近。此外，Mn的添加有利于提高共晶相和α(Al)基體相的形成溫度，有利于多邊形富鐵相的形成。

Different Mn contents were added to A356 aluminum alloy containing 1.0% Fe (mass fraction). The effects of Mn/Fe mole ratio on the iron-rich phase morphology were studied by analysis methods of OM, SEM, EDS and DSC, and the solidification sequence of phases in A356 alloy with Mn adding was investigated. The results show that the evolution order of the iron-rich phase morphology is needle-like, Chinese script, dendritic, starlike, polygonal with the increase of Mn/Fe mole ratio. The needle-iron phase is eliminated basically when Mn/Fe mole ratio is above 1.2. The (Fe, Mn)/Si mole ratio increases with iron-rich phase morphology solidification sequence namely, 0.5 to 0.7 in needle iron-rich phase, 1.2 to 1.7 in Chinese script and dendritic-like iron-rich phase, 1.9 in star-like and polygons-like iron-rich phase. With increasing the mole ratio, the average grain size and volume fraction of iron-rich phase increase firstly, then decrease and finally increase. The average grain size and volume fraction of the iron-rich phase are the minimum at Mn/Fe mole ratio of 1.0, similar to those of the A356-1.0Fe alloy. Furthermore, Mn addition is beneficial to increase the solidification temperature of eutectic phase and forming temperature of α(Al) matrix phase, thus promoting the forming of polygonal iron rich phase.

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