(西北工業(yè)大學(xué) 凝固技術(shù)國家重點(diǎn)實(shí)驗(yàn)室， 西安 710072)
摘 要: 采用丁二腈 - 水透明模型合金， 通過實(shí)時觀察技術(shù)對半固態(tài)處理過程中的組織形成及演化機(jī)理進(jìn)行了研究。結(jié)果表明， 球晶是由液相形核長大產(chǎn)生的， 而非由傳統(tǒng)形成機(jī)制——斷裂枝晶鈍化控制； 并且半固態(tài)處理過程中剪切速率顯著影響球晶的形成和分布。 隨著攪動速率提高，球化率逐步降低， 當(dāng)攪動速率足夠高時， 無球化發(fā)生； 同時， 球化率對攪動速率的突變非常敏感， 攪動速率的突變?nèi)菀自斐汕蚓У拇罅啃魏松L。
關(guān)鍵字: 半固態(tài)處理； 凝固組織； 丁二腈 - 水；球晶
（State Key Laboratory of Solidification Processing，Northwestern Polytechnical University， Xi′an 710072, P.R.China）
Abstract:The microstructure formation during semisolidmaterial processing was experimentally studied through direct observation in a transparent model alloy， succinonitrile5% water(mole fraction)， whose solidification is very similar to that of metals. The results show that the globular crystals form in the direct nucleation from theliquid phase， instead of from fragments of broken dendrites, and the shearing rate during stirring has an important influence on the globular formation. With increasing stirring rate, the ratio of globular formation decreases. When the stirring rate increases to a certain value, globular formation will not happen. The ratio of globular formation is highly sensitive to the sudden change of the stirring rate which causes the numerous nucleation and growth of globularcrystals.
Key words: semisolid material processing; solidification structure; succinonitrilewater; globular crystals
