【摘要】 研究了AZ91D镁合金在不同浇铸温度下组织的对比 ,以及稍低于液相线的近液相线铸造时静置时间和不同冷却能力铸模对铸态组织形貌的影响·结果表明 ,浇铸温度高于液相线时 ,降低浇铸温度有利于减轻镁合金的组织疏松 ,但组织粗大 ,此趋势持续到液相线上沿 ;而在稍低于液相线浇铸时 ,组织明显细化 ,有蔷薇化趋势 ,不再有高于液相线铸造时的显微气孔·在稍低于液相线温度时 ,适当静置有利于组织细化 ,一定程度上的枝晶熔断促进了蔷薇化 ,但不显著 ,静置时间过长 ,晶粒又有长大趋势 ,且出现个别异常长大枝晶·冷却速率对铸造组织的影响与静置时间有相近规律更多还原

【Abstract】 The as cast microstructures of AZ91D magnesium alloy were studied at various casting temperatures. The effects of stewing time and cooling capacity of mould on the cast structure of AZ91D alloy were investigated for near liquidus casting processing. When the casting temperature is above the liquidus, lower temperature is favor of lightening microstructure loose, however, coarser structure is obtained. This trend continues till the upper edge of liquidus. On the contrary, near liquidus casting promotes the microstructure refining and rosettizing, and the microporosity is invisible. The proper stewing time enhances the refining. The dendrite fusing at certain extent promotes the rosettization, however, over stewing is not expected. Increasing cooling rate has the similar effect on cast structure as that of increasing stewing time.更多还原