Ta元素对Nb-22Si-20Ti-6Mo合金微观组织和力学性能的影响

Effect of Ta Element on Microstructure and Mechanical Properties of Nb-22Si-20Ti-6Mo Alloy

摘要:

通过真空非自耗电弧熔炼制备了不同Ta含量的Nb-22Si-20Ti-6Mo-xTa（x=0，1，2，3，4，at%）合金，研究了Ta元素对合金相组成、微观组织和力学性能的影响。结果表明，Ta元素的添加不会改变Nb-22Si-20Ti-6Mo-xTa合金的相组成。所有合金均由Nbss和β-Nb₅Si₃组成，Ta主要固溶在Nbss中。合金微观组织由大块的初生β-Nb₅Si₃相和Nbss/β-Nb₅Si₃共晶组成，Ta元素细化了微观组织，初生β-Nb₅Si₃相的晶粒尺寸从26.84 μm下降到了14.65 μm。随着合金中Ta的增加，初生相的体积分数减少，共晶组织含量增多。合金的室温压缩强度随着Ta元素含量的增加得到了提高，当Ta元素的添加量从0提高到4at%时，合金的抗压强度从2261 MPa提高到2321 MPa。合金的断裂应变随着Ta含量增加呈先降后升的趋势，Ta含量为0的合金的断裂应变为9.9%，Ta含量为1at%的合金的断裂应变降至9.7%，Ta含量为4at%的合金的断裂应变增至最大值为10.6%。Ta元素的加入通过固溶强化和细晶强化机制提高抗压强度。由于合金组织的细化以及共晶组织的增多，提高了断裂应变。

Abstract:

Nb-22Si-20Ti-6Mo-xTa (x=0, 1, 2, 3, 4, at%) alloys with different contents of Ta were prepared by vacuum non-consumable arc melting method, and effects of Ta content on phase constitution, microstructure and mechanical properties of Nb-22Si-20Ti-6Mo-xTa alloys were investigated. Results show that addition of Ta does not change the phase composition Nb-22Si-20Ti-6Mo-xTa alloys. All alloys consist of Nbss and β-Nb₅Si₃, and Ta is mainly dissolved in Nbss. Microstructure of alloys consists of bulk primary β-Nb₅Si₃ phase and Nbss/β-Nb₅Si₃ eutectic. Addition of Ta refines the microstructure, and the grain size of primary β-Nb₅Si₃ phase decreases from 26.84 μm to 14.65 μm. In addition, the amount of primary phase is decreased with increasing the Ta content, and the amount of eutectic structure is increased. Room-temperature compressive strength of Nb-22Si-20Ti-6Mo-xTa alloys is improved with increasing the Ta content, and it is increased from 2261 MPa to 2321 MPa with increasing the Ta content from 0at% to 4at%. Fracture strain of Nb-22Si-20Ti-6Mo-xTa alloys first decrease and then increase with increasing the Ta content. Fracture strain of NST-0Ta alloy is 9.9%, that of NST-1Ta alloy is 9.7%, and that of NST-4Ta alloy increases to a maximum of 10.6%. Compressive strength improvement of alloys is contributed to solid solution strengthening and grain refinement strengthening by the addition of Ta. Due to refinement of alloy microstructure and the increase in eutectic structure, fracture strain of alloy is increased.