The present study was performed on A356 and B319 alloys in mechanically stirred or degassed condition. Melts were Sr-modified and grain-refined. Hydrogen content was varied from less than 0.1?ml/100?g Al to ～0.4?ml/100?g Al; Fe was increased to 0.8% in B319 alloy. Lanthanum and cerium were added as 99.5% pure metals. Two main techniques were used to investigate porosity formation: fracture surface of tensile or fatigue test bars, or reduced pressure test (RPT) method. Porosity type and shape were examined. The results show that pore size is more influential than small scattered ones from a mechanical point of view. Tensile testing is affected by porosity located at the center of the testing bar, whereas edge porosity is responsible for crack initiation in case of fatigue testing. Intermetallics precipitate in the form of intercepted platelets which restricts the flow of the molten metal, leading to formation of shrinkage cavities. Precipitation of clusters of compounds from the liquid state such as Al 2 Si 2 Sr, Mg 2 Sn, Al 3 Ti, or added Al 2 O 3 particles would as well act as nucleation sites for porosity formation. Most oxides were observed in the form of long branched strings. In some cases, bifilms were also reported in addition to SrO and MgO.
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机译：在机械搅拌或脱气的条件下对A356和B319合金进行本研究。融化是SR改性和晶粒精制的。氢含量从小于0.1？ml / 100·g Al至约0.4ml / 100·g al; B319合金的Fe增加到0.8％。加入镧和铈作为99.5％纯金属。使用两种主要技术来研究孔隙率形成：拉伸或疲劳试验棒的断裂表面，或减压测试（RPT）方法。检查孔隙型和形状。结果表明，孔径比机械的角度比小散射更有影响力。拉伸检测受位于检测杆中心的孔隙率的影响，而边缘孔隙率在疲劳试验的情况下负责裂纹启动。金属间化合物以截止的血小板形式沉淀，其限制熔融金属的流动，导致形成收缩腔。诸如Al 2 Si 2 Sr，Mg 2 Sn，Al 3 Ti的液态的化合物簇的沉淀，或添加Al 2 O 3颗粒，也可以作为孔隙率形成的成核位点。以长分支串的形式观察到大多数氧化物。在某些情况下，除了SRO和MgO之外还报告了BIFILMS。
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