The formation of entrainment defects, (also known as double oxide film defects or bifilms), caused by the entrapment of a doubled-over surface oxide film containing a small amount of local atmosphere, has been investigated by combining practical experiments using a commercial-purity Mg-alloy under protective gases, with theoretical thermodynamic calculations. Evolution of the entrainment defects was studied, and a double-layered structure of their oxide films was found, which was different from the single-layered structure of the Mg-alloy melt surface films that have been previously reported. A pore gas analyzer was used to analyze the gas trapped within the defects from which H₂ and N₂ (from the air) were detected. It was found that entrapped gases can be depleted through reactions with the surrounding liquid Mg-alloy, resulting in the oxide films growing together in the melt. Transformation of the entrained gas to solid-phase compounds could reduce the void volume of the defects, thus probably diminishing the negative effect of the entrainment defects on the quality of castings.

夹带缺陷（也称为双氧化膜缺陷或双膜）的形成，是由包含少量局部气氛的双表面氧化膜的夹带引起的，已通过结合使用商业纯度的实际实验进行了研究保护气体下的镁合金，具有理论热力学计算。研究了夹带缺陷的演变过程，发现其氧化膜呈双层结构，不同于以往报道的镁合金熔体表面膜的单层结构。孔隙气体分析仪用于分析缺陷中捕获的气体，其中 H ₂和 N ₂（从空气中）被检测到。发现夹带的气体可以通过与周围液态镁合金的反应耗尽，导致氧化膜在熔体中一起生长。夹带气体转化为固相化合物可以减少缺陷的空隙体积，从而可能减少夹带缺陷对铸件质量的负面影响。