(北京科技大學(xué) 材料科學(xué)與工程學(xué)院，北京 100083)
摘 要: 采用石墨質(zhì)蛇形通道制備半固態(tài)A380鋁合金漿料，研究漿料凝固過(guò)程中顯微組織的演變。結(jié)果表明：A380鋁合金熔體在蛇形通道內(nèi)發(fā)生一次凝固，在其通道內(nèi)壁激冷作用和異質(zhì)形核作用下形成大量的初生自由晶，半固態(tài)漿料的剩余液相在收集坩堝內(nèi)發(fā)生二次凝固形成二次非枝晶組織。初生晶粒的游離模型表明一部分初生自由晶直接生長(zhǎng)為球晶，其他部分則成長(zhǎng)為枝晶，枝晶在“自攪拌”的作用下發(fā)生縮頸和熔斷，通過(guò)“自旋轉(zhuǎn)”在蛇形通道內(nèi)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堝內(nèi)得到初步球化和熟化。同時(shí)，初生晶粒在收集坩堝內(nèi)得到進(jìn)一步球化、熟化和均勻分布，最終制備得到球狀晶粒均勻分布的半固態(tài)漿料。
關(guān)鍵字: A380鋁合金；半固態(tài)漿料；蛇形通道；顯微組織演變；二次凝固；游離模型
（School of Material Science and Engineer, University of Science and Technology Beijing, Beijing 100083, China）
Abstract:The semi-solid slurry of A380 aluminum alloy was prepared by the graphite serpentine channel, and the microstructure evolution during the solidification was investigated. The result shows that the initial solidification occurs in the serpentine channel, a large number of primary free grains are generated in the alloy melt in the role of chilling and heterogeneous nucleation of the serpentine channel inner wall. The secondary non-dendrites are formed during the secondary solidification which occurs in the remaining alloy melt of the semisolid slurry in the collective crucible. The drifting mode of primary grains indicates that a part of primary free grains grow to the spherical grains directly, others develop to the dendrites, the “self-stirring” of the alloy melt make the dendrites neck and fuse, and the dendrites get initial spheroidization and ripening by the “self-rotating” in the serpentine channel. The secondary non-dendrites formed during the secondary solidification get the initial spheroidization and ripening in the collective crucible. Meanwhile, the primary grains get the further spheroidization, ripening and uniform distribution in the collective crucible. Finally, the semi-solid slurry with uniformly distributed spherical grains is obtained.
Key words: A380 aluminum alloy; semi-solid slurry; serpentine channel; microstructure evolution; secondary solidification; drifting mode
