蛇形通道制备半固态A380铝合金浆料组织的演变

采用石墨质蛇形通道制备半固态A380铝合金浆料,并研究浆料制备过程中浆料组织的演变. 结果显示,合金熔体在蛇形通道内发生一次凝固,在其通道内壁的激冷和异质形核作用下形成大量的初生自由晶,半固态浆料的剩余液相在收集坩埚内发生二次凝固形成二次非枝晶. 初生晶粒的游离模型表明一部分初生自由晶直接生长为球晶,其他部分则成长为枝晶,枝晶在"自搅拌"的作用下发生缩颈和熔断,通过"自旋转"在蛇形通道内得到初步球化和熟化. 二次凝固形成的二次非枝晶在收集坩埚内得到初步球化和熟化,同时初生晶粒在收集坩埚内得到进一步球化、熟化和均匀分布.

Microstructure evolution of the A380 aluminum alloy semi-solid slurry prepared by serpentine channel

The semi-solid slurry of A380 aluminum alloy was prepared by using a graphite serpentine channel and the microstruc-ture evolution during solidification was investigated. The result showed that, initial solidification occurred in the serpentine channel, and a large number of primary free grains generated in the alloy melt under the influence of chilling and heterogeneous nucleation caused by the serpentine channel inner wall. Secondary non-dendrites formed during secondary solidification which occurred in the remaining alloy melt of the semi-solid slurry in the collective crucible. The drifting model of primary grains displayed that a part of primary free grains directly grew to spherical grains, and others developed to dendrites. The "self-stirring" of the alloy melt made dendrites neck and fuse, and they got initial spheroidization and ripening through the "self-rotating" in the serpentine channel. Secondary non-dendrites formed during secondary solidification got initial spheroidization and ripening in the collective crucible. Mean-while, the primary grains got further spheroidization, ripening and uniform distribution in the collective crucible.