求翻译：研究 粉粒度及真空度对AZ91D镁合金消失模铸造表面合金化过程的影响。同时，对真空度影响表面合金化的机制做了初步探索，发现抽真空形成的负压能增加镁合金液的渗流动力，而且真空度存在一个处于0.02 0.04 的临界值。真空度过小，EPS泡沫裂解产物将无法完全排出合金涂料层，导致表面合金化层会出现夹层现象；真空度过高则会引起合金化层产生孔洞，使得合金化表层性能不均匀。是什么意思？

The study of powder size and the degree of vacuum disappear the az91d magnesium alloy mold casting surface alloying process. The same time on the vacuum surface alloying mechanism to do a preliminary exploration, the negative pressure vacuum formed to increase the magnesium alloy liquid seepage forc

Research toner granularity and vacuum to 91 AZ D magnesium die cast away surface alloying process. Meanwhile, the vacuum surface alloying effects the mechanism to do a preliminary exploration and found that the vacuum-formed under pressure in the fluid of the magnesium to increase power, and seeping

Research powder granularity and vacuum degree to AZ91D magnesium alloy vanishing die casting tabulation surface alloy process influence.At the same time, machine has made the preliminary exploration to the vacuum degree influence surface alloy, discovered pulls out the negative pressure which the va

Study on particle size and vacuum degree on AZ91D magnesium alloy lost foam casting surface alloying effect. At the same time, the influencing mechanism of surface alloying of vacuum was a preliminary exploration, discovered vacuum negative pressure increases the formation of magnesium seepage of fl

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