NbおよびAl薄板から作製されたNb/Nb-Al金属間化合物積層材料における金属間化合物層の形成挙動

抄録

Laminate materials of Nb/Nb-aluminide were in-situ fabricated with pure Nb and Al foils by hot pressing. A pressure of 15 MPa was applied at the final temperature of the four-step heat treatment cycle, and this process made the multi-layered materials where Nb and Nb-aluminide layers were well bonded. The major phase of the layer was identified to be NbAl₃ phase by X-ray diffraction and SEM-EDS, and Nb₂Al phase was also formed in the interface of Nb and NbAl₃ layer. Therefore, the aluminide layer was stacked in the order of Nb/Nb₂Al/NbAl₃. The formation process of these phases is considered as, Nb(solid phase)+Al(solid phase)→Nb(solid phase)+Al(liquid phase)→Nb(solid phase)+NbAl₃(solid phase)→Nb(solid phase)+NbAl₃(solid phase)+Nb₂Al(solid phase). Nucleation and growth of the NbAl₃ phase in the first stage of the formation process is due to the solid Nb/liquid Al reaction, and the formation of the Nb₂Al layer in the second stage is caused by the diffusion of Nb into the NbAl₃ layer. The thickness of aluminide layers (NbAl₃ and Nb₂Al phase) well agreed with values calculated by the diffusion contorolled parabolic growth law.