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）

5

Si

3

and Al

3

Nb to Nbss、（Nb

Ti）

5

Si

3

、Ti and Al

3

Ti 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·m

1/2

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

-4

g

2

/（cm

4

·h）.After adding Ti

Ti

2

Nb

10

O

29

、TiNb

2

O

7

、TiO

2

and 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.