(河南理工大學(xué) 材料科學(xué)與工程學(xué)院，焦作 454000)
摘 要: 采用真空電弧熔煉水冷銅模吸鑄法制備Ni-50%Sc合金(摩爾分?jǐn)?shù)，下同)，采用程序計(jì)算、光學(xué)和掃描電子顯微鏡分析B2-NiSc金屬間化合物急冷快速凝固組織的演化規(guī)律，采用XRD和EDS分析合金組織的相組成。結(jié)果表明:以名義成分Ni-50%Sc配制合金，真空水冷銅模吸鑄成d 2、d 5和d 8 mm急冷試樣對(duì)應(yīng)的凝固速率分別為3112、497.9和194.5 K/s。Ro=1.5 mm為臨界尺寸，對(duì)應(yīng)著凝固速率的驟然變化。因Sc含量的損失，枝晶間出現(xiàn)了共晶(Ni2Sc+NiSc)組織；R＞Ro(d5和d 8 mm試樣)，凝固組織為粗大枝晶B2-NiSc+共晶(Ni2Sc+NiSc)組織；R＜Ro(d 2 mm試樣)為細(xì)小球狀枝晶B2-NiSc+少量共晶(Ni2Sc+NiSc)組織。經(jīng)Image-Pro Plus面積分析和計(jì)算，合金熔化過程中Sc燒損約為3.25%~3.31%，從理論上，通過亞快速凝固不能獲得單相B2-NiSc。急冷快速凝固后組織經(jīng)(970 ℃，72 h)均勻熱處理后，d 2 mm試樣組織為粒狀B2-NiSc+球狀顆粒Ni2Sc，d5和d8 mm組織為粒狀B2-NiSc+長條顆粒Ni2Sc。
關(guān)鍵字: 金屬間化合物；NiSc化合物；組織演化；急冷快速凝固
（School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China）
Abstract:Ni-50%Sc alloy was prepared with a vacuum arc smelting and water cooled copper mold suction-casting machine. The microstructure evolution of the rapidly solidified alloy which mainly consists of B2-NiSc phase was analyzed by optical metalloscopy and scanning electron microscopy. The microstructure constitutes was also calculated with an Image-Pro Plus software. XRD was used to identify phase microstructural components, and further more the composition of each phase was analyzed with EDS. The cooling rates for the solidified specimens with diameters of 2, 5 and 8 mm were 3112, 497.9 and 194.5 K/s, respectively. It is found that Ro=3/2 mm is a critical dimension which corresponds to an abrupt change in solidification rate. It is also found that eutectic mixture structure of (Ni2Sc+NiSc) is dispersed at grain boundary or between dendritic arms due to the loss of Sc element during melting. While R＞Ro (corresponding to the specimens with diameters of 5 and 8 mm), the solidification structure consists with coarse B2-NiSc dendrite and eutectic (Ni2Sc+NiSc). While R＜Ro (corresponding to the specimens with diameter of 2 mm), the solidification structure consists with fine globular B2-NiSc dendrite and relatively small amounts of eutectic (Ni2Sc+NiSc). Based on the phase volumetric analyzing of the microstructure with an Image-Pro Plus software, the loss of Sc element during melting is about 3.25%~3.31% in according with specimens diameters. Therefore, it could be concluded that B2-NiSc intermetallics without any second phase is difficult to achieve under the condition of sub-rapid solidification. Microstructures underwent (970 ℃, 72 h) homogenization heat treatment of the rapid solidified specimens were analyzed. Spherical Ni2Sc particles are dispersed on the B2-NiSc matrix for the specimen with 2 mm diameter, but the second phase Ni2Sc is in plate shape for the specimens with 5 and 8 mm diameters.
Key words: intermetallics; NiSc alloy; microstructure evolution; rapidly solidification
