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用真空非自耗电弧熔炼制备了Nb-16Si-22Ti-2Hf-2Cr-2Al母合金锭,用Y_2O_3坩埚真空感应熔炼对母合金锭重熔,浇入温度梯度约为4℃/mm,底部有铜板的Y_2O_3模壳,制备出直径60mm,长170mm的合金锭.考察了合金性能与组织特征的关系,探讨了硅化物对室温抗拉强度和高温压缩性能的影响.结果表明,Nb-Si双相复合材料中两相的组织特征对冷却速率非常敏感,初生相的选择和相组成均与冷却速率有关.大的冷却速率容易导致生成Nb_3Si相.随着冷却速率的减小,板条状Nb_3Si相的体积分数逐渐减少,有消失的趋势,初生相将变成块状Nb_5Si_3;共晶组织含量明显增加,Nbss枝晶尺寸增大,尤其是二次枝晶臂尺寸增大.细小均匀的两相共晶组织有利于提高合金的室温拉伸性能,板条状初生Nb_3Si相明显降低合金的室温拉伸性能,但适当数量、大小和形态的硅化物有利于提高合金的高温压缩强度.当铸锭由细小共晶组成时,其抗拉强度为449 MPa,相应的延伸率可以达到0.3%;当Nb_3Si含量在50%,宽度在80μm且平行于压缩方向时,合金在1250℃的高温压缩强度最高,为650 MPa.
Nb-16Si-22Ti-2Hf-2Cr-2Al master alloy ingot was prepared by vacuum non-consumable arc melting. The mother alloy ingot was remelted by vacuum induction melting with Y_2O_3 crucible. The pouring temperature gradient was about 4 ℃ / Y2 O3 mold shell with copper plate was prepared to prepare the alloy ingot with diameter of 60 mm and length of 170 mm.The relationship between the properties of the alloy and the microstructure was investigated and the influence of silicide on the tensile strength and compressibility at room temperature was discussed.The results showed that Nb- The microstructure and properties of two phases in two-phase composites are very sensitive to the cooling rate. The selection and phase composition of the primary phases are all related to the cooling rate. The large cooling rate easily leads to the formation of Nb_3Si phase. As the cooling rate decreases, The volume fraction of Nb 3 Si phase decreases and disappears gradually, and the primary phase becomes massive Nb 5 Si 3; the content of eutectic structure obviously increases and the size of Nbss dendrite increases, especially the size of secondary dendrite arm increases. The two-phase eutectic structure is conducive to improve the tensile properties of the alloy at room temperature, lath-shaped primary Nb 3 Si phase significantly reduce the tensile properties of the alloy at room temperature, but an appropriate amount, size and shape of the silicide is conducive to increasing the high temperature compressive strength alloy. Ingot by the fine When the Nb 3 Si content is 50%, the width is 80μm and parallel to the compression direction, the compressive strength of the alloy at 1250 ℃ is the highest, 650 MPa.