AZ91D镁合金组织细化及其对部分重熔半固态组织的影响

通过对熔体进行高强度剪切处理,研究了其对AZ91D镁合金的组织细化作用,获得了不同的铸锭组织,并研究了铸锭初始组织对二次加热后组织的影响.结果表明,熔体高强度剪切处理具有显著的晶粒细化作用,在650℃对熔体高强度剪切处理后,AZ91D镁合金铸锭平均晶粒尺寸由500μm降到170μm.降低熔体处理温度至605℃,组织得到进一步细化,平均晶粒尺寸约为60μm.原始组织大小对二次加热后组织的大小、液相分布具有重要的影响.熔体高强度剪切处理对AZ91D镁合金铸锭的晶粒细化作用在二次加热后能够基本保留下来.在相同的加热条件下,均匀细小的原始组织有利于获得更高的有效液相分数和更趋于球形的晶粒组织.

Grain Refinement of AZ91D Magnesium Alloy and Its Effect on the Partially Remelted Semi-Solid Microstructure

Grain refinement of AZ91D alloy with intensive melt shearing and its effect on partially remelted semi-solid microstructure were studied.The results showed that the intensive melt shearing prior to solidification has a significant grain refining effect on AZ91D alloy,which can reduce the grain size of ingots cast at 650 ℃ from 500 μm to 170 μm and further to 60 μm when the melt is treated at lower temperature.The initial microstructure plays a very important role on the formation of partially remelted semi-solid structure.The grain refinement achieved by the intensive melt shearing can be remained after partial remelting.Under identical reheating conditions,the uniform and fine microstructure can result in higher effective liquid fraction and more spherical microstructure.