(中南大學(xué) 粉末冶金國家重點(diǎn)實(shí)驗(yàn)室，長沙 410083)
摘 要: 采用掃描電鏡和電子探針分別觀察了用水冷銅坩堝磁懸浮、Drop casting法所制備樣品及磁懸浮法大鑄錠樣的微觀組織。結(jié)果發(fā)現(xiàn)：磁懸浮法大鑄錠的微觀組織存在明顯的宏觀鑄造缺陷，基本沒有微觀缺陷；其微觀組織中有明顯的晶界，晶界上有塊狀的初生b(B2)相；其微觀組織具有典型的片層狀特征。Drop casting法鑄錠的組織特征為：顯微縮松；晶界不明顯；無塊狀的晶界初生β(B2)相，但存在著白色的網(wǎng)狀組織；沒有明顯的片層狀組織。磁懸浮法大錠重熔樣的微觀組織特征與Drop casting法鑄錠的組織特征相似。水冷銅坩堝磁懸浮與Drop casting法這兩種鑄造方法所得的微觀組織不同，其成因跟合金的冷卻速率有關(guān)，在特定的條件下兩者之間可以發(fā)生相互轉(zhuǎn)變。在1 450 ℃保溫2 h后淬冰鹽水后，磁懸浮法鑄錠微觀組織的轉(zhuǎn)變成與Drop casting法微觀組織相似的組織。磁懸浮法大錠樣在非自耗電弧爐上重熔時，其微觀組織與Drop casting錠的組織很相似，關(guān)鍵在于兩者的冷卻速率更為接近。
關(guān)鍵字: TiAl基合金；磁懸浮；drop casting；鑄造；淬火；(B2)相；片層組織；晶粒
（State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China）
Abstract:The microstructures of ingots produced by magnetic levitation cold crucible technique, drop casting technique and re-melting from magnetic levitation sample were observed under scanning electron microscope and electron probe. The results show that the samples produced by magnetic levitation cold crucible technique have apparent casting macro-defect and there is almost not any micro-defect. There is apparent grainboundary in the magnetic levitation ingot and there is primary block (B2) phase. The lamella of Ti-45Al-7Nb-0.4W-0.15B alloy is perfect. The samples produced by drop casting have micro-pores. There are not any apparent grainboundary and any primary block (B2) phase, but there is white net. There is not lamella in the ingot. The differences between magnetic levitation cold crucible technique and drop casting technique result from cooling velocity of molten and they can transform reciprocally under the specific condition. The microstructure of ingot produced by magnetic levitation likes that produced by drop casting after being kept at 1 450 ℃ for 2 h then quenched in iced salt solution. The microstructural features of drop casting cast are similar with those of re-melting cast of magnetic levitation ingot. Because they are very close in cooling velocity.
Key words: TiAl alloy; magnetic levitation; drop casting; cast; quenching; (B2) phase; lamellar structure; grain
