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采用光学显微镜、扫描电镜、EDS能谱和差热分析研究了Mg-3Al合金中AlMn中间相的形貌特征,以及Mn含量对碳质变质剂异质形核作用的影响机制。结果表明:加碳变质处理产生的碳化铝可成为a-Mg的有效形核核心;当合金中的Mn含量小于0.32%(质量分数)时,加碳变质处理能使a-Mg晶粒明显细化,最小平均晶粒尺寸达到66μm,此时形成大量细小的球状和杆状Al Mn中间相,有助于晶粒细化;但当Mn含量增加到0.56%时,形成更多粗大的十字花瓣状AlMn中间相。过量的溶质Mn易与A1_4C_3粒子结合形成不利于形核的Al-Mn-C-O复杂化合物,并导致a-Mg晶粒粗化。
The morphology of AlMn mesophase in Mg-3Al alloy and the effect of Mn content on the heterogeneous nucleation of carbon modifier were investigated by optical microscopy, scanning electron microscopy, EDS spectroscopy and differential thermal analysis. The results show that aluminum carbide produced by carbon modification can be the effective nucleation site of a-Mg. When the content of Mn in the alloy is less than 0.32% (mass fraction), the a-Mg grain can be obviously thinned The minimum average grain size reached 66μm. At this time, a large number of fine spherical and rod-shaped Al Mn mesophases were formed, which contributed to the grain refinement. However, when the Mn content increased to 0.56%, more coarse cross petals Like AlMn mesophase. Excess solute Mn is easy to combine with A1_4C_3 particles to form complex Al-Mn-C-O compound which is unfavorable for nucleation and lead to coarsening of a-Mg crystal grains.