Ti对Nb-20Si-5Al超高温合金性能的影响

采用放电等离子烧结法(SPS)制备了Nb-20Si-5Al-xTi(x=0,18,20,22,摩尔分数)超高温合金,研究了Ti加入量对Nb-20Si-5Al合金的室温断裂韧度和高温抗氧化性的影响。结果表明,随着Ti加入量的增加,超高温合金的相组成由Nbss、Nb₅Si₃和Al3Nb相转变成为Nbss、(Nb,Ti)5Si3和Ti相。Ti能明显改善Nb-20Si-5Al超高温合金的断裂韧度和高温抗氧化性能,随着Ti加入量的增加均先提高然后降低,在Ti加入量为20%时,合金断裂韧度最大,为7.41 MPa·m^1/2,相比未加Ti时提高了约56.9%,其高温氧化速率最低,为0.72×10^-4g²/(cm⁴·h)。添加Ti元素后,其氧化产物中出现Ti₂Nb₁₀O₂₉、TiNb₂O₇、TiO₂等,可以提高其氧化膜的致密性,从而提高高温抗氧化性能。

Effects of Ti Addition on the Properties of Nb-20Si-5Al Ultrahigh Temperature Alloy

Nb-20Si-5Al-xTi(x=0,18,20,22,%)ultrahigh temperature alloys were prepared by the spark plasma sintering(SPS)technology.The effects of Ti addition on the fracture toughness and high temperature oxidation resistance of the alloys were analyzed.The results reveal that the phase composition of Nb-20Si-5Al ultrahigh temperature alloys is transformed from Nbss、(Nb,Ti)5Si3and Al3Nb to Nbss、(Nb,Ti)5Si3、Ti and Al3Ti phases.The fracture toughness and high temperature oxidation resistance of alloys can be obviously improved with the addition of Ti element,which are both increased firstly and then decreased with the increase of Ti content.When the content of Ti is 20%,the fracture toughness reaches the maximum value of 7.41MPa·m1/2,which is 56.9%higher than that of one without Ti,and the high temperature oxidation rate is the lowest,which is 0.72×10^-4g²/(cm⁴·h).After adding Ti,Ti₂Nb₁₀O₂₉、TiNb₂O₇、TiO₂and so on can be observed in the oxidation products,which improve the compactness of the oxide film,thus enhancing the oxidation resistance at high temperature.