(北京有色金屬研究總院 國家有色金屬復(fù)合材料工程技術(shù)研究中心， 北京 100088)
摘 要: 半固態(tài)材料具有非枝晶固相晶粒均勻分散懸浮于液態(tài)基體中的特殊結(jié)構(gòu)。提出了半固態(tài)材料中非枝晶組織的形成機(jī)制， 即“晶粒漂移和混和[CD*2]抑制機(jī)制”。 在電磁攪拌引起的強(qiáng)烈混和對流作用下，熔體的動態(tài)凝固過程不同于常規(guī)鑄造時的靜態(tài)凝固過程。 混和對流作用改變了熔體中的傳熱和傳質(zhì)過程， 從而決定了凝固組織。 晶粒漂移作用極大地增大了非均勻形核率， 從而細(xì)化晶粒；混和[CD*2]抑制作用則改變了晶粒生長形態(tài)， 使晶粒在各個方向上可以較為均勻地長大， 具有規(guī)則圓滑的形貌， 成為非枝晶組織。
關(guān)鍵字: 半固態(tài)加工； 非枝晶組織；電磁攪拌
（Beijing General Research Institute for Nonferrous Metals， Beijing 100088, P.R.China）
Abstract:The microstructure of semisolid metal comprises nondendritic solid phase grains suspended in liquid matrix, which is the key technological foundation for semisolid processing. In this paper, the formation mechanism for nondendritic structure in semisolid metal is proposed, namely mechanism of particledrift and blendingcompressing. Under vigorous convection caused by intense electromagnetic stirring, the dynamic solidification process of melt is quite different from that of conventional casting which is relatively static. The transferring of heat and mass during solidification is greatly changed by vigorous convection,and determined the microstructure. Particledrift greatly increases the heterogeneous nucleation and so refines the grains; Blendingcompressing changes the growing morphology of primary grains and makes grains grow relatively uniformly in all directions into near globular shape, and results in nondendritic structure.
Key words: semisolid processing； nondendritic structure； electromagnetic stirring
