Manganese-bearing intermetallic compounds (IMCs) are important for limiting micro-galvanic corrosion of magnesium-aluminum alloys and can initiate cracks under tensile load. Here, we use electron backscatter diffraction (EBSD), deep etching, and focussed ion beam (FIB) tomography to investigate the types of Al-Mn phases present, their faceted growth crystallography, and their three-dimensional distribution at different locations in high-pressure die cast (HPDC) AZ91D. The Al-Mn particle size distributions were well-described by lognormal distributions but with an additional population of externally solidified crystals (ESCs) formed in the shot chamber analogous to α-Mg ESCs. The large Al₈Mn₅ particles were cyclic twinned. Differences in the particle size distributions and number density in the center compared with the HPDC skin are identified, and the spatial relationship between Mg₁₇Al₁₂ and Al-Mn particles is explored.

含锰金属间化合物（IMC）对于限制镁铝合金的微电流腐蚀非常重要，并且在拉伸载荷下会引发裂纹。在这里，我们使用电子背散射衍射（EBSD），深蚀刻和聚焦离子束（FIB）断层扫描技术来研究存在的Al-Mn相的类型，其多面生长晶体学以及它们在高位不同位置的三维分布。压铸（HPDC）AZ91D。通过对数正态分布可以很好地描述Al-Mn粒度分布，但在弹丸室中形成了类似于α-MgESC的大量外部凝固晶体（ESC）。大Al ₈ Mn ₅颗粒是环状孪晶。确定了与HPDC蒙皮相比，中心的粒径分布和数量密度的差异，并探索了Mg ₁₇ Al ₁₂和Al-Mn颗粒之间的空间关系。